Search

Cr2O3 is an exceptional antiferromagnet with an easy axis of anisotropy that exhibits a magnetoelectric effect at room temperature [1]. Although there are technological challenges to use it for applications because of the relatively low bulk Neel temperature of TN = 308 K, there are demonstrations that TN can be substantially enhanced by strain in thin films. The morphology and growth procedure of such samples allow the appearance of flexomagnetic effects and pinning of domain walls at grain boundaries [2,3]. Here, we propose a material model of granular antiferromagnetic films and apply it to maze-like domain patterns in thin Cr2O3 samples [4]. The domain pattern is obtained by means of the nitrogen vacancy magnetometry and compared with spin-lattice simulations. We analyze the statistics of the size and self-similarity of the domain wall patterns to correlate the experimental measurements with the parameters of the theoretical model and compare the domain wall patterns with predictions made by a machine learning approach. The estimated inter-grain coupling is characterized by a substantial reduction of the effective exchange coupling to about 10% of the bulk value, with a wide standard deviation. Based on the material model, we provide design rules for the granular AFM recording media.

Antiferromagnets (AFMs) as materials with a high degree of magnetic compensation and complex dynamics attract attention for fundamental research and use in high-speed and low-energy-cosuming electronics. Technologically relevant AFM thin films usually possess a granular crystal structure, which alters the properties of domain walls and skyrmions [1,2]. Here, we provide a material model of a granular AFM and describe domain wall pinning at grain boundaries [3]. The model is applied to Cr2O3 films with a maze-like domain pattern visualized using nitrogen vacancy magnetometry. Using the statistical analysis of domain size and measuring the self-similarity parameters of the domain wall pattern, we estimate the material parameters characterizing the inter-grain coupling. Namely, for the films with a grain size of about 50 nm, the distribution of exchange bonds between grains is characterized by an average of 10% from the bulk value and a wide standard deviation, including a small amount of ferromagnetic bonds. The presented approach is compatible with machine learning techniques. Based on the material model, we provide design rules for the granular AFM recording media. [1] Jing et al, Phys. Rev. B 103, 174430 (2021) [2] Veremchuk et al, ACS Appl. El. Mat. 4, 2943 (2022); Erickson et al, RCS Adv. 13, 178 (2023) [3] Pylypovskyi et al, Phys. Rev. Appl. 20, 014020 (2023)

Thin films of magnetoelectric antiferromagnetic insulators (Cr2O3, BiFeO3 etc.) have emerged as a prospective material platform for magnonics, spin superfluidity, THz spintronics, and energy efficient spin-orbitronics. Understanding the magnetomechanical coupling in antiferromagnets offers vast advantages in the control of the primary order parameters. A standard micromagnetic approach for the description of a material relies on the effective parameters being homogeneously distributed throughout the system. Such an approach is commonly sufficient, but does not provide full characterization of the system. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the flexomagnetic effects promises technological advantages for multiferroic and antiferromagnetic materials, where cross-coupling between elastic, magnetic and electric subsystems open additional degrees of freedom in the control of the respective order parameters [1, 2]. In this work, we discover the effect of strain gradient onto the magnetic behaviour of epitaxial Cr2O3 thin films [3, 4]. We demonstrate that by tuning the parameters of Cr2O3 epitaxial growth a fine control of the crystallographic and defect structure can be realized. A persistent strain gradient was obtained in Cr2O3 affecting its magnetic order parameters rendering a distribution of the Néel temperature along the thickness of the thin film. The antiferromagnetic ordering in the strained films can persist up to 100°C, rendering Cr2O3 as a prospective material for industrial electronics applications. The inhomogeneous enhancement of the antiferromagnetic order parameter induced by the strain gradient renders a flexomagnetic response of about 15 µB nm-2. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic

Magneto-electric antiferromagnets are candidate materials for future spintronic devices. While antiferromagnets offer high speed, low power consumption and robustness to external fields, magneto-electrics allow manipulation of the magnetic order parameter not only via magnetic signals, but also via electric signals [1, 2]. Readout and manipulation of the antiferromagnetic order on the nanoscale typically relies on local probes sensitive to the surface magnetization. Therefore, its optimization is key challenge in device engineering. Here we investigate the surface magnetization of an oblique cut of single crystal Cr 2 O3 using scanning probe nitrogen-vacancy center magnetometry. The (104) surface normal is at an angle of 38.5° to the uniaxial anisotropy axis of Cr 2 O3. By magneto-electric annealing [3], a homogeneous antiferromagnetic order is initialized. We then measure the stray magnetic fields produced by topographic steps fabricated by ICP etching. The steps have various angles with respect to the c-axis in-surface component, allowing us to probe different `cuts` of the magnetization. We finally consider a simple model based on a homogenous surface magnetization strength and orientation for the various crystal facets. We find good agreement between this model and the recorded stray fields for a magnetization aligned with the bulk c-axis orientation. The predicted magnitude agrees with previous results of measurements on (001) surfaces [4]. We hope that these findings may aid in understanding the relation between surface and bulk magnetic order in antiferromagnets and aid in the development of antiferromagnetic spintronic devices.

Thin films of antiferromagnetic insulators (Cr2O3, Fe2O3, NiO etc.) are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A standard micromagnetic approach for the description of thin film system commonly relies on the effective parameters, assumed to be homogeneously distributed within a material. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the strain-gradient-driven magnetomechanical coupling promises technological advantages: the cross-coupling between elastic, magnetic and electric subsystems opens additional degrees of freedom in the control of the respective order parameters [1]-[3]. In this work, we discover the presence of flexomagnetic effects in epitaxial antiferromagnetic Cr2O3 thin films [4]. We demonstrate that a gradient of mechanical strain affect the order-disorder magnetic phase transition resulting in the distribution of the Néel temperature along the thickness of Cr2O3 thin film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15 µB nm-2. The antiferromagnetic ordering in the strained films can persist up to 100 °C, rendering Cr2O3 as a prospective material for industrial spintronic applications. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.

Understanding behavior of magnetic texture in antiferromagnetic nanostructures and thin films is crucial for the design of novel magnetic data storage and logic devices. Here, we derive the boundary conditions for the Néel vector in a two-sublattice antiferromagnet (AFM) and apply them to describe the shape of the domain walls [1,2] and skyrmions [2] in confined samples. In general, the surface of a 3D domain wall behaves as an elastic ribbon which bends in response on the topographic features of the single crystal Cr2 O3 [1]. In presence of the Dzyaloshinskii-Moriya interaction, topologically non-trivial AFM textures possess broadening near the surface. In thin films, the sample’s granularity becomes crucial. We present a model of a granular AFM and, by comparison with Nitrogen Vacancy magnetometry of 200-nm-thick Cr2O3 films, estimate the inter-grain exchange strength. The grain boundaries act as strong pinning sites for the AFM texture. [1] N. Hedrich et al., Nat. Phys. 17, 574 (2021); [2] O. Pylypovskyi et al., Phys. Rev. B 103, 134413 (2021).

Thin films of antiferromagnetic insulators are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and nonvolatile data storage. Here, we explore the presence of flexomagnetic effects in epitaxial Cr2O3 [1]. We demonstrate that a gradient of mechanical strain effect the order-disorder magnetic phase transition, resulting in the distribution of the Néel temperature along the thickness of a Cr2O3 film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15µB nm−2. The antiferromagnetic ordering in the strained films can persist up to 100∘C, rendering Cr2O3 as a prospective material for industrial electronics applications.

Thin films of antiferromagnetic insulators (Cr2O3, NiO etc.) are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A standard micromagnetic approach for the description of such thin films relies on the effective parameters being homogeneously distributed along the film thickness. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the magnetomechanical coupling promises technological advantages: the cross-coupling between elastic, magnetic and electric subsystems opens additional degrees of freedom in the control of the respective order parameters [1, 2, 3]. In this work, we discover the presence of flexomagnetic effects in epitaxial Cr2O3[4]. We demonstrate that a gradient of mechanical strain affect the order-disorder magnetic phase transition resulting in the distribution of the Neel temperature along the thickness of a Cr2O3 film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15 µB nm-2. The antiferromagnetic ordering in the strained films can persist up to 100°C, rendering Cr2O3 as a prospective material for industrial electronics applications. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.

Antiferromagnetic ordering, being prevalent over ferromagnetic one in nature, is very sensitive to the lattice structure. For example, in the absence of magnetostatics, the stress fields can be responsible for the domain formation in easy-plane antiferromagnets, while the hydrostatic pressure provides a possibility to manipulate the phase transition temperature between magnetically ordered and disordered phases [1]. Phenomena related to the strain gradient being allowed in the majority of magnetic symmetry classes are much less explored [2].Here, we provide a theoretical and experimental evidence of flexomagnetism in the uniaxial room-temperature antiferromagnet Cr2O3 [3]. In the experiment, high-quality Cr2O3 thin films grown on sapphire substrate are considered. Their magnetic state is accessed by a combination of magnetotransport measurements and Nitrogen vacancy (NV) magnetometry, which allows one to address both the uncompensated magnetization at the film surface and the interior of the film. We found a gradual transition from antiferro- to paramagnetic state by thickness with heating, which is substantially enhanced in comparison with bulk Cr2O3. To explain this observation, we provide a systematic analysis of sources of magnetization and symmetry analysis regarding the presence of a sizeable strain gradient along the film thickness. The latter enables (i) the net uniform bulk magnetization along the film thickness, which cannot be directly detected by NV magnetometry, and (ii) distribution of the Neel temperature along the film thickness. The gradual change of the magnetic phase transition temperature along the sample breaks the compensation of antiferromagnetic sublattices. The respective magnetization is proportional to the Neel vector and changes its direction betwen antiferromagnetic domains contributing to the stray fields and being detectable by NV magnetometry. We provide a theoretical description of this strain-gradient-driven effects in thin Cr2O3 fi

A search for high-speed and low-energy memory devices puts antiferromagnetic thin films at the forefront of spintronic research. Here, we develop a material model of a granular antiferromagnetic thin film with uniaxial anisotropy and provide fundamental insight into the interaction of antiferromagnetic domain walls with grain boundaries. This model is validated on thin films of the antiferromagnetic insulator \ch{Cr2O3}, revealing complex maze-like domain patterns hosting localized nanoscale domains down to 50 nm. We show that the inter-grain magnetic parameters can be estimated based on an analysis of high-resolution images of antiferromagnetic domain patterns examining the domain patterns' self-similarity and the statistical distribution of domain sizes. Having a predictive material model and understanding of the pinning of domain walls on grain boundaries, we put forth design rules to realize granular antiferromagnetic recording media.

Thin films of antiferromagnetic insulators (Cr2O3, Fe2O3, NiO etc.) are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A standard micromagnetic approach for the description of thin film system commonly relies on the effective parameters, assumed to be homogeneously distributed within a material. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the strain-gradient-driven magnetomechanical coupling promises technological advantages: the cross-coupling between elastic, magnetic and electric subsystems opens additional degrees of freedom in the control of the respective order parameters [1]-[3]. In this work, we discover the presence of flexomagnetic effects in epitaxial antiferromagnetic Cr2O3 thin films [4]. We demonstrate that a gradient of mechanical strain affect the order-disorder magnetic phase transition resulting in the distribution of the Néel temperature along the thickness of Cr2O3 thin film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15 µB nm-2. The antiferromagnetic ordering in the strained films can persist up to 100 °C, rendering Cr2O3 as a prospective material for industrial spintronic applications. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.

Thin films of antiferromagnetic insulators (Cr2O3, NiO etc.) are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A standard micromagnetic approach for the description of such thin films relies on the effective parameters being homogeneously distributed along the film thickness. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the magnetomechanical coupling promises technological advantages: the cross-coupling between elastic, magnetic and electric subsystems opens additional degrees of freedom in the control of the respective order parameters [1, 2, 3]. In this work, we discover the presence of flexomagnetic effects in epitaxial Cr2O3[4]. We demonstrate that a gradient of mechanical strain affect the order-disorder magnetic phase transition resulting in the distribution of the Neel temperature along the thickness of a Cr2O3 film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15 µB nm-2. The antiferromagnetic ordering in the strained films can persist up to 100°C, rendering Cr2O3 as a prospective material for industrial electronics applications. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.

Thin films of magnetoelectric antiferromagnetic insulators (Cr2O3, BiFeO3 etc.) have emerged as a prospective material platform for magnonics, spin superfluidity, THz spintronics, and energy efficient spin-orbitronics. Understanding the magnetomechanical coupling in antiferromagnets offers vast advantages in the control of the primary order parameters. A standard micromagnetic approach for the description of a material relies on the effective parameters being homogeneously distributed throughout the system. Such an approach is commonly sufficient, but does not provide full characterization of the system. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the flexomagnetic effects promises technological advantages for multiferroic and antiferromagnetic materials, where cross-coupling between elastic, magnetic and electric subsystems open additional degrees of freedom in the control of the respective order parameters [1, 2]. In this work, we discover the effect of strain gradient onto the magnetic behaviour of epitaxial Cr2O3 thin films [3, 4]. We demonstrate that by tuning the parameters of Cr2O3 epitaxial growth a fine control of the crystallographic and defect structure can be realized. A persistent strain gradient was obtained in Cr2O3 affecting its magnetic order parameters rendering a distribution of the Néel temperature along the thickness of the thin film. The antiferromagnetic ordering in the strained films can persist up to 100°C, rendering Cr2O3 as a prospective material for industrial electronics applications. The inhomogeneous enhancement of the antiferromagnetic order parameter induced by the strain gradient renders a flexomagnetic response of about 15 µB nm-2. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic

Understanding behavior of magnetic texture in antiferromagnetic nanostructures and thin films is crucial for the design of novel magnetic data storage and logic devices. Here, we derive the boundary conditions for the Néel vector in a two-sublattice antiferromagnet (AFM) and apply them to describe the shape of the domain walls [1,2] and skyrmions [2] in confined samples. In general, the surface of a 3D domain wall behaves as an elastic ribbon which bends in response on the topographic features of the single crystal Cr2 O3 [1]. In presence of the Dzyaloshinskii-Moriya interaction, topologically non-trivial AFM textures possess broadening near the surface. In thin films, the sample’s granularity becomes crucial. We present a model of a granular AFM and, by comparison with Nitrogen Vacancy magnetometry of 200-nm-thick Cr2O3 films, estimate the inter-grain exchange strength. The grain boundaries act as strong pinning sites for the AFM texture. [1] N. Hedrich et al., Nat. Phys. 17, 574 (2021); [2] O. Pylypovskyi et al., Phys. Rev. B 103, 134413 (2021).

Thin films of antiferromagnetic insulators are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and nonvolatile data storage. Here, we explore the presence of flexomagnetic effects in epitaxial Cr2O3 [1]. We demonstrate that a gradient of mechanical strain effect the order-disorder magnetic phase transition, resulting in the distribution of the Néel temperature along the thickness of a Cr2O3 film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15µB nm−2. The antiferromagnetic ordering in the strained films can persist up to 100∘C, rendering Cr2O3 as a prospective material for industrial electronics applications.

Magneto-electric antiferromagnets are candidate materials for future spintronic devices. While antiferromagnets offer high speed, low power consumption and robustness to external fields, magneto-electrics allow manipulation of the magnetic order parameter not only via magnetic signals, but also via electric signals [1, 2]. Readout and manipulation of the antiferromagnetic order on the nanoscale typically relies on local probes sensitive to the surface magnetization. Therefore, its optimization is key challenge in device engineering. Here we investigate the surface magnetization of an oblique cut of single crystal Cr 2 O3 using scanning probe nitrogen-vacancy center magnetometry. The (104) surface normal is at an angle of 38.5° to the uniaxial anisotropy axis of Cr 2 O3. By magneto-electric annealing [3], a homogeneous antiferromagnetic order is initialized. We then measure the stray magnetic fields produced by topographic steps fabricated by ICP etching. The steps have various angles with respect to the c-axis in-surface component, allowing us to probe different `cuts` of the magnetization. We finally consider a simple model based on a homogenous surface magnetization strength and orientation for the various crystal facets. We find good agreement between this model and the recorded stray fields for a magnetization aligned with the bulk c-axis orientation. The predicted magnitude agrees with previous results of measurements on (001) surfaces [4]. We hope that these findings may aid in understanding the relation between surface and bulk magnetic order in antiferromagnets and aid in the development of antiferromagnetic spintronic devices.

Antiferromagnetic ordering, being prevalent over ferromagnetic one in nature, is very sensitive to the lattice structure. For example, in the absence of magnetostatics, the stress fields can be responsible for the domain formation in easy-plane antiferromagnets, while the hydrostatic pressure provides a possibility to manipulate the phase transition temperature between magnetically ordered and disordered phases [1]. Phenomena related to the strain gradient being allowed in the majority of magnetic symmetry classes are much less explored [2].Here, we provide a theoretical and experimental evidence of flexomagnetism in the uniaxial room-temperature antiferromagnet Cr2O3 [3]. In the experiment, high-quality Cr2O3 thin films grown on sapphire substrate are considered. Their magnetic state is accessed by a combination of magnetotransport measurements and Nitrogen vacancy (NV) magnetometry, which allows one to address both the uncompensated magnetization at the film surface and the interior of the film. We found a gradual transition from antiferro- to paramagnetic state by thickness with heating, which is substantially enhanced in comparison with bulk Cr2O3. To explain this observation, we provide a systematic analysis of sources of magnetization and symmetry analysis regarding the presence of a sizeable strain gradient along the film thickness. The latter enables (i) the net uniform bulk magnetization along the film thickness, which cannot be directly detected by NV magnetometry, and (ii) distribution of the Neel temperature along the film thickness. The gradual change of the magnetic phase transition temperature along the sample breaks the compensation of antiferromagnetic sublattices. The respective magnetization is proportional to the Neel vector and changes its direction betwen antiferromagnetic domains contributing to the stray fields and being detectable by NV magnetometry. We provide a theoretical description of this strain-gradient-driven effects in thin Cr2O3 fi

Magneto-electric antiferromagnets hold promise for future spintronic devices, as they offer magnetic field hardness, high switching speeds and both electric and magnetic control of their order parameters, owing to the magneto-electric coupling [1]. As information and functionality is encoded in the antiferromagnetic order parameter, its manipulation, read-out and nanoscale textures are paramount for device operation, as well as interesting from a fundamental point of view. For applications the surface plays a key-role as the interface often dictates the read/write functionalities and gains importance as thin film devices are targeted. Using scanning nitrogen vacancy magnetometry [2] we study a ‘textbook’, single crystal magneto-electric antiferromagnet Cr 2O3 and perform nanoscale imaging of its surface magnetization, which is directly linked to its magnetic order parameter. We first confirm magneto-electric poling [3] of a homogeneous antiferromagnetic order and study the stray field polarity at the surface depending on the used field configuration. Our results are consistent with a theoretically predicted topmost disordered layer [4]. In the next step local electrodes are utilized to nucleate individual single domain walls. Manipulation of the domain wall path is demonstrated both by local laser heating, as well as the creation of an energy landscape for the domain wall position via topographic structuring [2]. Analysing the domain wall path yields further information about the boundary conditions for the order parameter at topographic edges and an estimate of the full 3D-profile of the texture based on minimizing the domain walls surface energy. A Snell like refraction of the domain wall path is found, that can be represented in an analytical approximation as a ‘refractive index’ for a given island dimension as demonstrated for a range of incidence angles. The demonstrated pinning and control of the domain wall position constitutes the main ingredients for logic

Magneto-electric antiferromagnets hold promise for future spintronic devices, as they offer magnetic field hardness, high switching speeds and both electric and magnetic control of their order parameters, owing to the magneto-electric coupling [1]. As information and functionality is encoded in the antiferromagnetic order parameter, its manipulation, read-out and nanoscale textures are paramount for device operation, as well as interesting from a fundamental point of view. For applications the surface plays a key-role as the interface often dictates the read/write functionalities and gains importance as thin film devices are targeted. Using scanning nitrogen vacancy magnetometry [2] we study a ‘textbook’, single crystal magneto-electric antiferromagnet Cr 2O3 and perform nanoscale imaging of its surface magnetization, which is directly linked to its magnetic order parameter. We first confirm magneto-electric poling [3] of a homogeneous antiferromagnetic order and study the stray field polarity at the surface depending on the used field configuration. Our results are consistent with a theoretically predicted topmost disordered layer [4]. In the next step local electrodes are utilized to nucleate individual single domain walls. Manipulation of the domain wall path is demonstrated both by local laser heating, as well as the creation of an energy landscape for the domain wall position via topographic structuring [2]. Analysing the domain wall path yields further information about the boundary conditions for the order parameter at topographic edges and an estimate of the full 3D-profile of the texture based on minimizing the domain walls surface energy. A Snell like refraction of the domain wall path is found, that can be represented in an analytical approximation as a ‘refractive index’ for a given island dimension as demonstrated for a range of incidence angles. The demonstrated pinning and control of the domain wall position constitutes the main ingredients for logic

Magneto-electric antiferromagnets hold promise for future spintronic devices, as they offer magnetic field hardness, high switching speeds combined with electric and magnetic control of their order parameters, owing to the magneto-electric coupling [1]. As information and functionality is encoded in the antiferromagnetic order parameter, its manipulation, read-out and nanoscale texture are paramount for device operation, as well as interesting from a fundamental point of view. E.g. spin-textures in such materials are theorized to carry an intrinsic magnetization [2]. Here we study a single crystal ‘textbook’ magneto-electric antiferromagnet, Cr2O3, by nanoscale imaging of its surface magnetization via magnetic stray field imaging by scanning nitrogen vacancy magnetometry [3]. This surface magnetization is directly linked to the bulk Neel vector of Cr2O3 and thereby allows for nanoscale imaging of antiferromagnet spin textures. After confirming magneto-electric poling [4], local electrodes are utilized to nucleate single domain walls, which we then study on the nanometer scale. Manipulation of the domain wall is demonstrated both by local laser heating [5], as well as the creation of an energy landscape for the domain wall via topographic structuring [3]. We analyze the interaction of the domain wall with topographic islands both experimentally and in simulations. This analysis yields information about the domain wall boundary conditions at topographic edges and an estimate of the full 3D-profile of the texture based on minimizing the domain walls surface energy. A Snell like refraction of the domain wall path is found, that can be represented in an analytical approximation as a ‘refractive index’ for a given island dimension as demonstrated for a range of incidence angles. We then observe bistable domain wall paths configurations and switching between them is demonstrated and imaged experimentally. This pinning and control of the domain wall position constitutes the

Antiferromagnets (AFMs) have regained strong attention from the magnetism community especially with the advent of antiferromagnetic spintronics [1]. The key operational element of spintronic devices is represented by information carriers, such as domain walls (DWs) and skyrmions. The simplest AFM DW separates two regions with the opposite orientation of the Neel order parameter. Although highly relevant, the experimental studies of AFM DWs (visualization, dynamics, mechanics) are challenging because of strict requirements on measurement techniques to access their properties. Here, we overcome these limitations and conduct detailed, quantitative studies of the mechanics and the nanoscale properties of individual, antiferromagnetic DWs in a single crystal Cr2O3 – a room-temperature, magnetoelectric, insulating AFM [2]. Our results reveal a remarkably pristine DW behaviour, which is governed by DW energy minimization and boundary conditions, but largely unaffected by pinning or disorder – a “textbook example” of antiferromagnetic DW physics. In our experiment, the crystal’s (0001) surface is patterned by a grid of mesas with mean thickness and width t=166 nm and w=2400 nm, respectively. The DW is nucleated by means of magnetoelectric field cooling by inverting the electric bias field over opposite halves of the sample. The DW may also be dragged through the mesa pattern by a focused laser spot. The magnetic texture is imaged using Nitrogen Vacancy (NV) magnetometry [3]. We find that the DW mimics an elastic surface with specific mechanical properties, determined by the interaction with the topographic features of the sample where the DW is (i) deflected from the straight plane crossing the mesa; (ii) bent around mesa corners. To address the DW behaviour theoretically, we perform large-scale spin-lattice simulations with GPU speed-up [4]. The analytical Ansatz is developed based on the numerically-obtained, three-dimensional DW profile. All main features of the DW behav

Antiferromagnets offer remarkable promise for future spintronics devices, where antiferromagnetic order is exploited to encode information. The control and understanding of antiferromagnetic domain walls (DWs) - the interfaces between domains with differing order parameter orientations - is a key ingredient for advancing such antiferromagnetic spintronics technologies. However, studies of the intrinsic mechanics of individual antiferromagnetic DWs remain elusive since they require sufficiently pure materials and suitable experimental approaches to address DWs on the nanoscale. Here we nucleate isolated, 180° DWs in a single-crystal of Cr2O3, a prototypical collinear magnetoelectric antiferromagnet, and study their interaction with topographic features fabricated on the sample. We demonstrate DW manipulation through the resulting, engineered energy landscape and show that the observed interaction is governed by the DW's elastic properties. Our results advance the understanding of DW mechanics in antiferromagnets and suggest a novel, topographically defined memory architecture based on antiferromagnetic DWs.

Magneto-electric antiferromagnets hold promise for future spintronic devices, as they offer magnetic field hardness, high switching speeds combined with electric and magnetic control of their order parameters, owing to the magneto-electric coupling [1]. As information and functionality is encoded in the antiferromagnetic order parameter, its manipulation, read-out and nanoscale texture are paramount for device operation, as well as interesting from a fundamental point of view. E.g. spin-textures in such materials are theorized to carry an intrinsic magnetization [2]. Here we study a single crystal ‘textbook’ magneto-electric antiferromagnet, Cr2O3, by nanoscale imaging of its surface magnetization via magnetic stray field imaging by scanning nitrogen vacancy magnetometry [3]. This surface magnetization is directly linked to the bulk Neel vector of Cr2O3 and thereby allows for nanoscale imaging of antiferromagnet spin textures. After confirming magneto-electric poling [4], local electrodes are utilized to nucleate single domain walls, which we then study on the nanometer scale. Manipulation of the domain wall is demonstrated both by local laser heating [5], as well as the creation of an energy landscape for the domain wall via topographic structuring [3]. We analyze the interaction of the domain wall with topographic islands both experimentally and in simulations. This analysis yields information about the domain wall boundary conditions at topographic edges and an estimate of the full 3D-profile of the texture based on minimizing the domain walls surface energy. A Snell like refraction of the domain wall path is found, that can be represented in an analytical approximation as a ‘refractive index’ for a given island dimension as demonstrated for a range of incidence angles. We then observe bistable domain wall paths configurations and switching between them is demonstrated and imaged experimentally. This pinning and control of the domain wall position constitutes the

Antiferromagnets (AFMs) have regained strong attention from the magnetism community especially with the advent of antiferromagnetic spintronics [1]. The key operational element of spintronic devices is represented by information carriers, such as domain walls (DWs) and skyrmions. The simplest AFM DW separates two regions with the opposite orientation of the Neel order parameter. Although highly relevant, the experimental studies of AFM DWs (visualization, dynamics, mechanics) are challenging because of strict requirements on measurement techniques to access their properties. Here, we overcome these limitations and conduct detailed, quantitative studies of the mechanics and the nanoscale properties of individual, antiferromagnetic DWs in a single crystal Cr2O3 – a room-temperature, magnetoelectric, insulating AFM [2]. Our results reveal a remarkably pristine DW behaviour, which is governed by DW energy minimization and boundary conditions, but largely unaffected by pinning or disorder – a “textbook example” of antiferromagnetic DW physics. In our experiment, the crystal’s (0001) surface is patterned by a grid of mesas with mean thickness and width t=166 nm and w=2400 nm, respectively. The DW is nucleated by means of magnetoelectric field cooling by inverting the electric bias field over opposite halves of the sample. The DW may also be dragged through the mesa pattern by a focused laser spot. The magnetic texture is imaged using Nitrogen Vacancy (NV) magnetometry [3]. We find that the DW mimics an elastic surface with specific mechanical properties, determined by the interaction with the topographic features of the sample where the DW is (i) deflected from the straight plane crossing the mesa; (ii) bent around mesa corners. To address the DW behaviour theoretically, we perform large-scale spin-lattice simulations with GPU speed-up [4]. The analytical Ansatz is developed based on the numerically-obtained, three-dimensional DW profile. All main features of the DW behav

Antiferromagnets have recently emerged as attractive platforms for spintronics applications, offering fundamentally new functionalities compared with their ferromagnetic counterparts. Whereas nanoscale thin-film materials are key to the development of future antiferromagnetic spintronic technologies, existing experimental tools tend to suffer from low resolution or expensive and complex equipment requirements. We offer a simple, high-resolution alternative by addressing the ubiquitous surface magnetization of magnetoelectric antiferromagnets in a granular thin-film sample on the nanoscale using single-spin magnetometry in combination with spin-sensitive transport experiments. Specifically, we quantitatively image the evolution of individual nanoscale antiferromagnetic domains in 200 nm thin films of Cr2O3 in real space and across the paramagnet-to-antiferromagnet phase transition, finding an average domain size of 230 nm, several times larger than the average grain size in the film. These experiments allow us to discern key properties of the Cr2O3 thin film, including the boundary magnetic moment density, the variation of critical temperature throughout the film, the mechanism of domain formation, and the strength of exchange coupling between individual grains comprising the film. Our work offers novel insights into the magnetic ordering mechanism of Cr2O3 and firmly establishes single-spin magnetometry as a versatile and widely applicable tool for addressing antiferromagnetic thin films on the nanoscale.

Nitrogen vacancy microscopy is used to detect tiny magnetic stray fields from antiferromagnetic Cr2O3 thin films. Domains and domain dynamics are reported.

thin films of antiferromagnets are notably different than bulk crystals.

thin films of antiferromagnets are notably different than bulk crystals.

MERAM based on Cr2O3/Pt is presented

MERAM based on Cr2O3/Pt is presented

[This corrects the article DOI: 10.1186/s41512-016-0001-y.].

Magnetoelectric and purely antiferromagnetic RAM is shown based on Cr2O3/Pt

MERAM based on Cr2O3/Pt is presented

Extrinsic effects on Cr2O3 thin films are shown. Also a statistical method to evaluate AF domain pattern in an electric way is demonstrated.

MERAM based on Cr2O3/Pt is presented

Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy-efficiency. We propose and realize purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50 times lower writing threshold compared to ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we realize reliable isothermal switching via gate voltage pulses and all-electric read-back at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed and removed for read-out allowing permanent magnets to be used. Based on our prototypes of these novel systems, we construct a comprehensive model of the magnetoelectric selection mechanism in thin films of magnetoelectric antiferromagnets. We identify that growth induced effects lead to emergent ferrimagnetism, which interferes with the linear magnetoelectric effect. After pinpointing lattice misfit as the likely origin, we provide routes to enhance or mitigate this emergent ferrimagnetism as desired. AF-MERAM cells are a general concept for antiferromagnetic spintronics and not limited to memory applications.

Extrinsic effects on Cr2O3 thin films are shown. Also a statistical method to evaluate AF domain pattern in an electric way is demonstrated.

MERAM based on Cr2O3/Pt is presented

Magnetoelectric and purely antiferromagnetic RAM is shown based on Cr2O3/Pt

Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy efficiency. We propose and demonstrate a purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50 fold reduction of the writing threshold compared to ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal switching via gate voltage pulses and all-electric readout at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed for readout, allowing permanent magnets to be used. Based on our prototypes of these novel AF-MERAM elements, we construct a comprehensive model of the magnetoelectric selection mechanism in thin films of magnetoelectric antiferromagnets. We identify that growth induced effects lead to emergent ferrimagnetism, which is detrimental to the robustness of the storage. After pinpointing lattice misfit as the likely origin, we provide routes to enhance or mitigate this emergent ferrimagnetism as desired. Beyond memory applications, the AF-MERAM concept introduces a general all-electric interface for antiferromagnets and should find wide applicability in purely antiferromagnetic spintronics devices. In particular, the read out of the magnetic state is realized by Zero-Offset Hall [Kosub et al., Phys. Rev. Lett. 115, 097201 (2015)] which can detect the proximity magnetization that developes in metallic electrodes at the boundary of insulating antiferromagnets. This technique possesses considerable applicability to the field of antiferromagnetic spintronics, as it can probe the net magnetization of both metallic and insulating antiferromagnetic thin films.

Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy efficiency. We propose and demonstrate a purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50 fold reduction of the writing threshold compared to ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal switching via gate voltage pulses and all-electric readout at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed for readout, allowing permanent magnets to be used. Based on our prototypes of these novel AF-MERAM elements, we construct a comprehensive model of the magnetoelectric selection mechanism in thin films of magnetoelectric antiferromagnets. We identify that growth induced effects lead to emergent ferrimagnetism, which is detrimental to the robustness of the storage. After pinpointing lattice misfit as the likely origin, we provide routes to enhance or mitigate this emergent ferrimagnetism as desired. Beyond memory applications, the AF-MERAM concept introduces a general all-electric interface for antiferromagnets and should find wide applicability in purely antiferromagnetic spintronics devices. In particular, the read out of the magnetic state is realized by Zero-Offset Hall [Kosub et al., Phys. Rev. Lett. 115, 097201 (2015)] which can detect the proximity magnetization that developes in metallic electrodes at the boundary of insulating antiferromagnets. This technique possesses considerable applicability to the field of antiferromagnetic spintronics, as it can probe the net magnetization of both metallic and insulating antiferromagnetic thin films.

Circulating levels of adiponectin, a hormone produced predominantly by adipocytes, are highly heritable and are inversely associated with type 2 diabetes mellitus (T2D) and other metabolic traits. We conducted a meta-analysis of genome-wide association studies in 39,883 individuals of European ancestry to identify genes associated with metabolic disease. We identified 8 novel loci associated with adiponectin levels and confirmed 2 previously reported loci (P = 4.5×10(-8)-1.2×10(-43)). Using a novel method to combine data across ethnicities (N = 4,232 African Americans, N = 1,776 Asians, and N = 29,347 Europeans), we identified two additional novel loci. Expression analyses of 436 human adipocyte samples revealed that mRNA levels of 18 genes at candidate regions were associated with adiponectin concentrations after accounting for multiple testing (p<3×10(-4)). We next developed a multi-SNP genotypic risk score to test the association of adiponectin decreasing risk alleles on metabolic traits and diseases using consortia-level meta-analytic data. This risk score was associated with increased risk of T2D (p = 4.3×10(-3), n = 22,044), increased triglycerides (p = 2.6×10(-14), n = 93,440), increased waist-to-hip ratio (p = 1.8×10(-5), n = 77,167), increased glucose two hours post oral glucose tolerance testing (p = 4.4×10(-3), n = 15,234), increased fasting insulin (p = 0.015, n = 48,238), but with lower in HDL-cholesterol concentrations (p = 4.5×10(-13), n = 96,748) and decreased BMI (p = 1.4×10(-4), n = 121,335). These findings identify novel genetic determinants of adiponectin levels, which, taken together, influence risk of T2D and markers of insulin resistance.

Body fat distribution, particularly centralized obesity, is associated with metabolic risk above and beyond total adiposity. We performed genome-wide association of abdominal adipose depots quantified using computed tomography (CT) to uncover novel loci for body fat distribution among participants of European ancestry. Subcutaneous and visceral fat were quantified in 5,560 women and 4,997 men from 4 population-based studies. Genome-wide genotyping was performed using standard arrays and imputed to ~2.5 million Hapmap SNPs. Each study performed a genome-wide association analysis of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), VAT adjusted for body mass index, and VAT/SAT ratio (a metric of the propensity to store fat viscerally as compared to subcutaneously) in the overall sample and in women and men separately. A weighted z-score meta-analysis was conducted. For the VAT/SAT ratio, our most significant p-value was rs11118316 at LYPLAL1 gene (p = 3.1 × 10E-09), previously identified in association with waist-hip ratio. For SAT, the most significant SNP was in the FTO gene (p = 5.9 × 10E-08). Given the known gender differences in body fat distribution, we performed sex-specific analyses. Our most significant finding was for VAT in women, rs1659258 near THNSL2 (p = 1.6 × 10-08), but not men (p = 0.75). Validation of this SNP in the GIANT consortium data demonstrated a similar sex-specific pattern, with observed significance in women (p = 0.006) but not men (p = 0.24) for BMI and waist circumference (p = 0.04 [women], p = 0.49 [men]). Finally, we interrogated our data for the 14 recently published loci for body fat distribution (measured by waist-hip ratio adjusted for BMI); associations were observed at 7 of these loci. In contrast, we observed associations at only 7/32 loci previously identified in association with BMI; the majority of overlap was observed with SAT. Genome-wide association for visceral and subcutaneous fat revealed a SNP for VAT in

Paramyxovirus assembly at the cell membrane requires the movement of viral components to budding sites and envelopment of nucleocapsids by cellular membranes containing viral glycoproteins, facilitated by interactions with the matrix protein. The specific protein interactions during assembly of respiratory syncytial virus (RSV) are unknown. Here, the postulated interaction between the RSV matrix protein (M) and G glycoprotein (G) was investigated. Partial co-localization of M with G was demonstrated, but not with a truncated variant lacking the cytoplasmic domain and one-third of the transmembrane domain, in cells infected with recombinant RSV or transfected to express G and M. A series of G mutants was constructed with progressively truncated or modified cytoplasmic domains. Data from co-expression in cells and a cell-free binding assay showed that the N-terminal aa 2-6 of G play a key role in G-M interaction, with serine at position 2 and aspartate at position 6 playing key roles. © 2005 SGM.

OBJECTIVE: Insulin-induced phosphatidylinositol 3-kinase (PI3K)/Akt signaling and interleukin-6 (IL-6)-instigated JAK/STAT3-signaling pathways in the liver inhibit the expression of gluconeogenic genes to decrease hepatic glucose output. The insulin receptor (IR) and JAK1 tyrosine kinases and STAT3 can serve as direct substrates for the T-cell protein tyrosine phosphatase (TCPTP). Homozygous TCPTP-deficiency results in perinatal lethality prohibiting any informative assessment of TCPTP's role in glucose homeostasis. Here we have used Ptpn2+/- mice to investigate TCPTP's function in glucose homeostasis. RESEARCH DESIGN AND METHODS: We analyzed insulin sensitivity and gluconeogenesis in chow versus high-fat-fed (HFF) Ptpn2+/- and Ptpn2+/+ mice and insulin and IL-6 signaling and gluconeogenic gene expression in Ptpn2+/- and Ptpn2+/+ hepatocytes. RESULTS: HFF Ptpn2+/- mice exhibited lower fasted blood glucose and decreased hepatic glucose output as determined in hyperinsulinemic euglycemic clamps and by the decreased blood glucose levels in pyruvate tolerance tests. The reduced hepatic glucose output coincided with decreased expression of the gluconeogenic genes G6pc and Pck1 and enhanced hepatic STAT3 phosphorylation and PI3K/Akt signaling in the fasted state. Insulin-induced IR-beta-subunit Y1162/Y1163 phosphorylation and PI3K/Akt signaling and IL-6-induced STAT3 phosphorylation were also enhanced in isolated Ptpn2+/- hepatocytes. The increased insulin and IL-6 signaling resulted in enhanced suppression of G6pc and Pck1 mRNA. CONCLUSIONS: Liver TCPTP antagonises both insulin and STAT3 signaling pathways to regulate gluconeogenic gene expression and hepatic glucose output.

The matrix protein of paramyxoviruses plays an important role in virus assembly through its interactions with cell membrane, virus envelope and virus nucleocapsid. In the present study, we investigated the possible association of respiratory syncytial virus (RSV) matrix (M) protein with the plasma membrane of infected cells. Using confocal microscopy we found that M was present at the cytoplasmic side of the plasma membrane. We used flotation gradients to purify membranes from RSV infected cells and treated them with cold Triton X-100 to obtain lipid rafts in the insoluble fraction. Western blot of the lipid raft fraction with specific antibodies showed that it contained M, as well as G (attachment) and N (nucleocapsid) proteins. We also found that RSV purified on sucrose gradients contained lipid raft markers. Together, our data suggest that RSV uses lipid rafts for assembly and budding.

Respiratory syncytial virus (RSV) G glycoprotein mediates cell attachment through surface glycosaminoglycans (GAGs). Feldman et al. [10] suggested that specific basic amino acids in residues 184-198 of G defined a critical heparin binding domain (HBD). To further define the G HBD we made a series of truncated G proteins expressed in Escherichia coli. G88 (G residues 143-231), bound to HEp-2 cells in a dose dependent manner and binding was inhibited >99% with heparin. Cell binding of G88 was unaltered by alanine substitution mutagenesis of all basic amino acids in Feldman's region 184-198. A G88 variant truncated beyond residue 198, G58, and G58 fully alanine substituted in the region 184-198, G58A6, bound to HEp-2 cells about half as well and 100-fold less well than G88, respectively. G88 and all alanine substitution mutants of G88 inhibited RSV plaque formation by 50% (ID50) at concentrations of ~50 nM; the ID50 of G58 was ~425 nM while G58A6 had an ID50 > 1600 nM. These data show that the G HBD includes as much as residues 187-231, that there is redundancy beyond the previously described HBD, and that the cell-binding and virus infectivity-blocking functions of these recombinant G proteins were closely linked and required at least one HBD.

The matrix protein of paramyxoviruses plays an important role in virus assembly through its interactions with cell membrane, virus envelope and virus nucleocapsid. In the present study, we investigated the possible association of respiratory syncytial virus (RSV) matrix (M) protein with the plasma membrane of infected cells. Using confocal microscopy we found that M was present at the cytoplasmic side of the plasma membrane. We used flotation gradients to purify membranes from RSV infected cells and treated them with cold Triton X-100 to obtain lipid rafts in the insoluble fraction. Western blot of the lipid raft fraction with specific antibodies showed that it contained M, as well as G (attachment) and N (nucleocapsid) proteins. We also found that RSV purified on sucrose gradients contained lipid raft markers. Together, our data suggest that RSV uses lipid rafts for assembly and budding.

Respiratory syncytial virus (RSV) G glycoprotein mediates cell attachment through surface glycosaminoglycans (GAGs). Feldman et al. [10] suggested that specific basic amino acids in residues 184-198 of G defined a critical heparin binding domain (HBD). To further define the G HBD we made a series of truncated G proteins expressed in Escherichia coli. G88 (G residues 143-231), bound to HEp-2 cells in a dose dependent manner and binding was inhibited >99% with heparin. Cell binding of G88 was unaltered by alanine substitution mutagenesis of all basic amino acids in Feldman's region 184-198. A G88 variant truncated beyond residue 198, G58, and G58 fully alanine substituted in the region 184-198, G58A6, bound to HEp-2 cells about half as well and 100-fold less well than G88, respectively. G88 and all alanine substitution mutants of G88 inhibited RSV plaque formation by 50% (ID50) at concentrations of ~50 nM; the ID50 of G58 was ~425 nM while G58A6 had an ID50 > 1600 nM. These data show that the G HBD includes as much as residues 187-231, that there is redundancy beyond the previously described HBD, and that the cell-binding and virus infectivity-blocking functions of these recombinant G proteins were closely linked and required at least one HBD.

Every commander in today's military forces is well aware of his ultimate responsibility for achieving unit readiness to ensure that the command is able, willing, and prepared to perform its mission, both in garrison and in combat. Inherent in this responsibility is the authority of the commander to assess unit readiness by inspecting areas, equipment, and personnel under his command. Frequently, however, a commander is criticized for allegedly violating the legal rights of subordinates in exercising his inspection authority. Until recently, disagreement, indecision, and the absence of any clear rules among military judges and court have only aggravated the commander's frustration. All too often a commander perceives himself to be confronted by a maze of inconsistent and self-defeating legal restrictions affecting his inspection authority. The purpose of this article is to examine the legal rights of a commander to inspect his command and the competing privacy rights of individual Service members in light of recent developments in military law. It is written with the commander in mind and is intended to assist him in removing the frustration and confusion surrounding his inspection authority.