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Strain exerted by a ferroelectric substrate on a thin ferromagnetic multilayer film is a promising low-energy method of controlling chiral magnetic spin textures. Here we report on the effect of strain coupling between magnetic domains in skyrmion-host multilayer Pt/CoFeB/Ir and ferroelectric domains in BaTiO3 substrates. By imaging the multilayer’s demagnetised domain pattern using wide-field Kerr microscopy we observe magnetic stripe domains with orientation aligned with the underling ferroelectric domain pattern. Upon cooling, the domain period changes abruptly at the BaTiO3 phase transition temperatures, indicating that the strain orients the stripe domains on the micrometre scale and also introduces sample-wide changes in magnetic properties such as anisotropy and exchange interaction strength. These results open a route to electric field control of the domain morphology and microscopic properties in thin multilayer structures that are already used as skyrmion hosts, and unlock the possibility of controlling skyrmion properties through electric fields alone.

We thank the Engineering and Physical Sciences Research Council (EPSRC UK) for support via Grants No. EP/M000923/1, No. EP/K036408/1, No. EP/I004483/1, No. EP/S031081/1, and No. EP/S030263/1. L.L., S.S., D.J. and G.T. acknowledge also support from STFC-ISIS Neutron and Muon Source and Ada Lovelace Centre at STFC-SCD. We acknowledge use of the ARCHER (via the U.K. Car–Parrinello Consortium, EP/P022618/1 and EP/P022189/2), U.K. Materials and Molecular Modelling Hub (EP/P020194/1), and STFC Scientific Computing Department's SCARF HCP facilities. We acknowledge support from the Henry Royce Institute. This work was also supported financially through the EPSRC Grant Nos. EP/ P022464/1, and EP/R00661X/1. Muonium is a combination of first- and second-generation matter formed by the electrostatic interaction between an electron and an antimuon (μ+). Although a well-known physical system, their ability to form collective excitations in molecules had not been observed. Here, we give evidence for the detection of a muonium state that propagates in a molecular semiconductor lattice via thermally activated dynamics: a muonium polaron. By measuring the temperature dependence of the depolarization of the muonium state in C60, we observe a thermal narrowing of the hyperfine distribution that we attribute to the dynamics of the muonium between molecular sites. As a result of the time scale for muonium decay, the energies involved, charge and spin selectivity, this quasiparticle is a widely applicable experimental tool. It is an excellent probe of emerging electronic, dynamic, and magnetic states at interfaces and in low dimensional systems, where direct spatial probing is an experimental challenge owing to the buried interface, nanoscale elements providing the functionality localization and small magnitude of the effects. Publisher PDF

Using scanning thermal microscopy, we have mapped the spatial distribution of temperatures in an operating nanoscale device formed from a magnetic injector, an Ag connecting wire, and a magnetic detector. An analytical model explained the thermal diffusion over the measured temperature range (2–300 K) and injector-detector separation (400–3000 nm). The characteristic diffusion lengths of the Peltier and Joule heat differ remarkably below 60 K, a fact that can be explained by the onset of ballistic phonon heat transfer in the substrate.

Combining magnetic and superconducting functionalities enables lower energy spin transfer and magnetic switching in quantum computing and information storage, owing to the dissipationless nature of quasi-particle mediated supercurrents. Here, we put forward a system where emergent spin-ordering and diffusion of Cooper pairs are achieved at a non-intrinsically magnetic nor superconducting metallo-molecular interface. Electron transport, magnetometry and low-energy muon spin rotation are used to probe time-reversal symmetry breaking in these structures. By comparing the Meissner expulsion in a system including a Cu/C60 spin-converter interface to one without, we observe a paramagnetic contribution that can be explained due to the conversion of spin-singlet Cooper pair states into odd-frequency triplet states. These results demonstrate the potential of metallo-molecular interfaces to achieve singlet to triplet Cooper pair conversion, a capability not present in either metal or molecule separately that could be used in the generation and controlled diffusion of spin polarised dissipationless currents. Magnetic molecules deposited on a metallic substrate constitute a method to engineer the spin properties of the molecule and has potential application in low-power information storage devices. Here, the authors investigate a superconductor/molecule/normal metal heterostructure and demonstrate spin-ordering and proximity induced superconducting properties at the metallo-molecular interface.

5d metals are used in electronics because of their high spin-orbit coupling (SOC) leading to efficient spin-electric conversion. When C60 is grown on a metal, the electronic structure is altered due to hybridization and charge transfer. In this work, we measure the spin Hall magnetoresistance for Pt/C60 and Ta/C60, finding that they are up to a factor of 6 higher than those for pristine metals, indicating a 20-60% increase in the spin Hall angle. At low fields of 1-30 mT, the presence of C60 increased the anisotropic magnetoresistance by up to 700%. Our measurements are supported by noncollinear density functional theory calculations, which predict a significant SOC enhancement by C60 that penetrates through the Pt layer, concomitant with trends in the magnetic moment of transport electrons acquired via SOC and symmetry breaking. The charge transfer and hybridization between the metal and C60 can be controlled by gating, so our results indicate the possibility of dynamically modifying the SOC of thin metals using molecular layers. This could be exploited in spin-transfer torque memories and pure spin current circuits.

Hybrid interfaces form a spin capacitor for the generation and storage of spin angular momentum via optical or electronic stimuli., We show that hybrid MnOx/C60 heterojunctions can be used to design a storage device for spin-polarized charge: a spin capacitor. Hybridization at the carbon-metal oxide interface leads to spin-polarized charge trapping after an applied voltage or photocurrent. Strong electronic structure changes, including a 1-eV energy shift and spin polarization in the C60 lowest unoccupied molecular orbital, are then revealed by x-ray absorption spectroscopy, in agreement with density functional theory simulations. Muon spin spectroscopy measurements give further independent evidence of local spin ordering and magnetic moments optically/electronically stored at the heterojunctions. These spin-polarized states dissipate when shorting the electrodes. The spin storage decay time is controlled by magnetic ordering at the interface, leading to coherence times of seconds to hours even at room temperature.

Unconventional superconductivity has been suggested to be present at the interface between bismuth and nickel in thin-film bilayers. In this work, we study the structural, magnetic, and superconducting properties of sputter deposited Bi/Ni bilayers. As-grown, our films do not display a superconducting transition; however, when stored at room temperature, after about 14 days our bilayers develop a superconducting transition up to 3.8 K. To systematically study the effect of low temperature annealing on our bilayers, we perform structural characterization with x-ray diffraction and polarized neutron reflectometry, along with magnetometry and low-temperature electrical transport measurements on samples annealed at 70∘C. We show that the onset of superconductivity in our samples is coincident with the formation of ordered NiBi3 intermetallic alloy, a known s-wave superconductor. We calculate that the annealing process has an activation energy of (0.86±0.06) eV. As a consequence, gentle heating of the bilayers will cause formation of the superconducting NiBi 3 at the Ni/Bi interface, which poses a challenge to studying any distinct properties of Bi/Ni bilayers without degrading that interface.

We thank the Engineering and Physical Sciences Research Council (EPSRC) in the United Kingdom for support through Grants EP/P001556/1, EP/J01060X/1, EP/I004483/1, and EP/M000923/1. R.S. wishes to acknowledge EPSRC for a scholarship via the Grant EP/L015110/1. XAS/XMCD experiments were performed in the BOREAS beamline at the Alba synchrotron (Proposals ID2014071101 and ID2015091530). M.V. acknowledges Mineco Grant FIS2013-45469-C4-3-R. Use of the N8 High Performance Computing (HPC) (EPSRC EP/K000225/1) and ARCHER (via the UK Car–Parrinello Consortium, EP/K013610/1 and EP/P022189/1) Charge transfer at metallo–molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc–C60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo–carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp3 orbitals are annealed into sp2−π graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher π*-molecular levels, whereas the dichroism in the σ*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz–π hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices. Postprint

We demonstrate a Josephson junction with a weak link containing two ferromagnets, with perpendicular magnetic anisotropy and independent switching fields in which the critical current can be set by the mutual orientation of the two layers. Such pseudospin-valve Josephson junctions are a candidate cryogenic memory in an all superconducting computational scheme. Here, we use Pt/Co/Pt/CoB/Pt as the weak link of the junction with $d_\text{Co} = 0.6$ nm, $d_\text{CoB} = 0.3$ nm, and $d_\text{Pt} = 5$ nm and obtain a $60\%$ change in the critical current for the two magnetization configurations of the pseudospin-valve. Ferromagnets with perpendicular magnetic anisotropy have advantages over magnetization in-plane systems which have been exclusively considered to this point, as in principle the magnetization and magnetic switching of layers in the junction should not affect the in-plane magnetic flux., Comment: 5 pages, 3 figures

Background: Low back pain (LBP) is one of the major factors impairing the quality of life and is the most frequent cause of disability. Inadequate water intake is believed to be the predisposing factor for LBP particularly in the younger population. It is commonly seen that the incidence of LBP has been on the rise in people between 20-40 years of age. Thus, the basic aim of this study is to find a potential relationship between dehydration and LBP among young adults. Methods: This cross-sectional study was conducted from the medical students and practicing doctors of 21-39 years from March-May 2019. Characteristics of pain along with the daily activities of patients were assessed. The severity was assessed by using the Graded Chronic pain scale (GCPS). Results: Out of a total of 426 participants, 84.74% had LBP. Of these, 44.3% complained of having it more than once a week, with duration usually between 1-7 days. More than half of the patients had their routines disturbed because of this pain. Most of the participants complained of an episodic increase in summers. The majority (75.9%, n=274) drank 5-9 glasses of water a day, 64.5% of them were of opinion that their daily water consumption was enough, while 61.5% felt an association between dehydration and LBP. According to the GCPS, one-third of the population had chronic pain of grade I and the other third had grade IV. Conclusion: It can be concluded that with the increase in the pace of life many individuals who belong to the above mentioned age group have a reduced intake of water, and due to a probable relationship between LBP and dehydration, this might be a reason of the increasing propensity of LBP in them. There is a need for further work in this regard.

Football is one of the most popular sports in the world. Many studies have shown there is a high incidence of gonarthrosis in football players. The reason for this increase is said to be injuries to the meniscus, the anterior cruciate ligament (ACL) and the resulting surgeries. The incidence is significantly increased in players with knee injuries. The knee is also the most commonly injured site in football and the most common cause of surgery in football players. Together these injuries, particularly of the ACL or meniscus and the resulting surgeries, increase the risk of developing gonarthrosis in post-football years.

Variegate porphyria (VP) is one of the groups of rare inherited disorders of hemoglobin synthesis called Porphyria. It has two distinct manifestations, that is, those of cutaneous and nervous system. Posterior reversible encephalopathy syndrome (PRES) is a rare complication of porphyria. It occurs due to vasogenic edema in white matter of predominantly parieto-occipital lobes, characterized by headache, visual disturbances, altered mental state, hypertension, and seizures. We report a child diagnosed with VP who presents with clinical signs and radiological manifestations suggestive of PRES. To our knowledge this has never been reported in a case of VP and only twice been reported in another type of porphyria. A 12-year-old pre-pubertal boy already diagnosed with VP presents with seizure, visual disturbance, altered mental status, headache, and hypertension. Initial brain magnetic resonance imaging (MRI) revealed bilateral increased signal intensity in parieto-occipital region. Neurological opinion suggested that the symptoms experienced by the patient seem to be a complication of porphyria. Treatment was to control hypertension and prevent use of any aggravating agents. Follow-up MRI after two weeks revealed interval reduction in disease process. Diagnosis of PRES was thus confirmed. PRES should be considered in patients presenting with symptoms typical of encephalitis/meningitis/acute disseminated encephalomyelitis in a patient suffering from porphyria. Early diagnosis is key to quick improvement and prevention of complications. Though rare in pre-pubertal patients, it should be kept as a possibility especially when patients present with hypertension. Care should be taken to not use any drugs that can trigger PRES.

Introduction Caring for a child with diabetes often has a negative effect on the mental health of caregivers and other family members. The goal of this study was to determine the effect of caring for children with diabetes on the mental health of caregivers. Materials and methods This case-control study was conducted in the National Institute of Child Health from October to November 2017 to compare the mental health effects associated with caring for children with diabetes as against caring for children without diabetes. The case group consisted of the caregivers of 60 children with diabetes, and the control group consisted of the caregivers of 60 children without diabetes. A validated questionnaire with two scales was used. Frequencies, percentages, confidence intervals, and p-values were reported for the categorical variables. The variables were analyzed using Patient Health Questionnaire 9 (PHQ-9) and Generalized Anxiety Disorder 7 (GAD-7) scales to determine associations. Results In the case group, most caregivers were mothers, 60% had consanguineous marriages, 21.7% were employed, and 21.7% were suffering from a long-term illness. Of those reporting a disease, 13.3% reported a change in their disease. Most caregivers (71.7%) received family support, and 78.3% of caregivers had social support. Most caregivers in the case group had mild depression, and 35% had mild anxiety. In the control group, most caregivers were mothers, 5% were employed, and 35% had disease(s). Of those reporting a disease, 15% reported a change in their health. Most of the caregivers in the control group (93.3%) had family support, and 85% had social support. Most (62%) were found to have mild depression, and more than half had no anxiety. Most children in the control group were under five years old, and most children in the case group were over 10 years old. Nearly half of the children in the case group had a positive family history of thalassemia, and 68.3% of them have insulin administered once daily. Strong variables that affect caregiver mental health were caregiver age, health changes, and consanguinity. Conclusion The caregivers of children with diabetes have a higher incidence of anxiety compared with the caregivers of children without diabetes; depression was similar for both groups. Health care providers should be aware of the differences in parenting stress related to caring for children with long-term illnesses and should consider ways to help improve the well-being of these caregivers.

Antiferromagnetic materials present us with rich and exciting physics, which we can exploit to open new avenues in spintronic device applications. We explore perpendicularly magnetized exchange biased systems of Pt/Co/IrMn and Pt/Co/FeMn, where the crossover from paramagnetic to antiferromagnetic behavior in the IrMn and FeMn layers is accessed by varying the thickness. We demonstrate, through magneto-optical imaging, that the magnetic domain morphology of the ferromagnetic Co layer is influenced by the N${\'e}$el order of the antiferromagnet (AFM) layers. We relate these variations to the anisotropy energy of the AFM layer and the ferromagnet-antiferromagnet (FM-AFM) inter-layer exchange coupling. We also quantify the interfacial Dzyaloshinskii-Moriya interaction (DMI) in these systems by Brillouin light scattering spectroscopy. The DMI remains unchanged, within experimental uncertainty, for different phases of the AFM layers, which allows us to conclude that the DMI is largely insensitive to both AFM spin order and exchange bias. Understanding such fundamental mechanisms is crucial for the development of future devices employing chiral spin textures, such as N${\'e}$el domain walls and skyrmions, in FM-AFM heterostructures.

We report measurements on yttrium iron garnet (YIG) thin films grown on both gadolinium gallium garnet (GGG) and yttrium aluminium garnet (YAG) substrates, with and without thin Pt top layers. We provide three principal results: the observation of an interfacial region at the Pt/YIG interface, we place a limit on the induced magnetism of the Pt layer and confirm the existence of an interfacial layer at the GGG/YIG interface. Polarised neutron reflectometry (PNR) was used to give depth dependence of both the structure and magnetism of these structures. We find that a thin film of YIG on GGG is best described by three distinct layers: an interfacial layer near the GGG, around 5 nm thick and non-magnetic, a magnetic bulk phase, and a non-magnetic and compositionally distinct thin layer near the surface. We theorise that the bottom layer, which is independent of the film thickness, is caused by Gd diffusion. The top layer is likely to be extremely important in inverse spin Hall effect measurements, and is most likely Y2O3 or very similar. Magnetic sensitivity in the PNR to any induced moment in the Pt is increased by the existence of the Y2O3 layer; any moment is found to be less than 0.02 uB/atom., 10 pages, 4 figures

The temperature dependence of the spin diffusion length typically reflects the scattering mechanism responsible for spin relaxation. Within nonmagnetic metals it is reasonable to expect the Elliot-Yafet mechanism to play a role and thus the temperature dependence of the spin diffusion length might be inversely proportional to resistivity. In lateral spin valves, measurements have found that at low temperatures the spin diffusion length unexpectedly decreases. By measuring the transport properties of lateral Py/Cu/Py spin valves, fabricated from Cu with magnetic impurities of $l1$ ppm and $\ensuremath{\sim}4$ ppm, we extract a spin diffusion length which shows this suppression below 30 K only in the presence of the Kondo effect. We have calculated the spin-relaxation rate and isolated the contribution from magnetic impurities. We find the spin-flip probability of a magnetic impurity to be 34%. Our analysis demonstrates the dominant role of Kondo scattering in spin relaxation, even in low concentrations of order 1 ppm, and hence illustrates its importance to the reduction in spin diffusion length observed by ourselves and others.

This short letter to the editor provides ideas about exercises that improves cardiovascular fitness.

Tapered coplanar waveguides with integrated photoconductors were designed, fabricated, and measured, with pulsed transmission results comparing well with High Frequency Structure Simulator simulations which predict increased confinement and electric field concentration in the tapered region. Devices made with titanium/gold metallisation were used to demonstrate transmission and confinement, while the magnetoresistive properties of devices with cobalt/copper multilayers were used to demonstrate the field concentration. In the latter case, a mathematical framework was developed to understand the relationship between tapering effects and the picosecond magnetoresistance response.

This work was supported by the Engineering and Physical Sciences Research Council through grants EP/K00512X/1, EP/K036408/1, EP/J01060X/1 and EP/I004483/1. Only three elements are ferromagnetic at room temperature: the transition metals iron, cobalt and nickel. The Stoner criterion explains why iron is ferromagnetic but manganese, for example, is not, even though both elements have an unfilled 3d shell and are adjacent in the periodic table: according to this criterion, the product of the density of states and the exchange integral must be greater than unity for spontaneous spin ordering to emerge. Here we demonstrate that it is possible to alter the electronic states of non-ferromagnetic materials, such as diamagnetic copper and paramagnetic manganese, to overcome the Stoner criterion and make them ferromagnetic at room temperature. This effect is achieved via interfaces between metallic thin films and C60 molecular layers. The emergent ferromagnetic state exists over several layers of the metal before being quenched at large sample thicknesses by the materiala € s bulk properties. Although the induced magnetization is easily measurable by magnetometry, low-energy muon spin spectroscopy provides insight into its distribution by studying the depolarization process of low-energy muons implanted in the sample. This technique indicates localized spin-ordered states at, and close to, the metal-molecule interface. Density functional theory simulations suggest a mechanism based on magnetic hardening of the metal atoms, owing to electron transfer. This mechanism might allow for the exploitation of molecular coupling to design magnetic metamaterials using abundant, non-toxic components such as organic semiconductors. Charge transfer at molecular interfaces may thus be used to control spin polarization or magnetization, with consequences for the design of devices for electronic, power or computing applications (see, for example, refs 6 and 7). Postprint

Cricket has transformed very quickly from a gentleman’s game to a game which demand high standard of physical and physiological fitness. Cricket has a diversity of game formats ranging from 5-day test cricket to a shorter but dynamic t20 format. Since last two decades a lot of cricket is being played throughout the year, there is no discrimination of summers and winters as what used to happen during the prior days. For this reason now the standard of physiological demands of this sport has risen too. Good heart rate is always an important aspect of physiological fitness of athletes and it has a mighty impact on the performance of players in the grounds.

We use ferromagnetic resonance to study the current-induced torques in YIG/heavy metal bilayers. YIG samples with thickness varying from 14.8 nm to 80 nm, with Pt or Ta thin film on top, are measured by applying a microwave current into the heavy metals and measuring the longitudinal DC voltage generated by both spin rectification and spin pumping. From a symmetry analysis of the FMR lineshape and its dependence on YIG thickness, we deduce that the Oersted field dominates over spin-transfer torque in driving magnetization dynamics., 8 pages, 3 figures

We report on the temperature dependence of the recently discovered spin Hall magnetoresistance in a yttrium iron garnet (YIG)/platinum (Pt) thin film. The YIG/Pt layers are an ideal choice as the combination of an insulating magnetic material and the high spin-orbit interaction in Pt gives a relatively large magnetoresistance and no electrical conduction occurs in the YIG. The temperature dependence of the magnetoresistance was measured between 1.4 K and 280 K from which the temperature dependence of the spin diffusion length in Pt has been extracted. We found that the best agreement between our data and the recently published [Chen, Phys. Rev. B 87, 144411 (2013)PRBMDO1098-012110.1103/ PhysRevB.87.144411] theory of the spin Hall magnetoresistance is given by an assumed Elliot-Yafet mechanism of spin relaxation with temperature-independent spin Hall angle and spin mixing conductance. The best estimate for the spin diffusion length returns values between 0.57 and 3.85 nm.

Time-resolved scanning Kerr microscopy (TRSKM) has been used to examine the effect of nonlocal spin transfer torque (NL-STT) within a two-terminal current perpendicular-to-plane nonlocal spin valve. A combination of Oersted field and NL-STT was used to excite and control the magnetization dynamics. By comparison with a macrospin model, the strength of the NL-STT was quantified and found to be comparable to that achieved by direct injection of spin-polarized current. The sensitivity of the magneto-optical probe to small out-of-plane deflections of the magnetization also allows the NL-STT to be quantified in quasi-dc measurements, greatly simplifying the investigation of STT phenomena.

Femtosecond optical pump-probe experiments were performed upon a Ni(720 A)/Si(100) sample in the polar geometry with the pump beam close to normal incidence. A signal due to the ultrafast demagnetization effect was observed when the pump pulse was linearly polarized. When the pump was elliptically polarized, additional peaks were observed at zero time delay, resulting from the specular inverse Faraday effect (SIFE) and the specular optical Kerr effect (SOKE). By comparing measurements made with different pump helicities, the SIFE and SOKE peaks and the demagnetization signal were found to superpose in a linear fashion. From the dependence of the peak height upon the pump polarization, values of χxxyy=(1−3i)×10−10 rad cm3 erg−1 and χxyyx=(−9+2i)×10−12 rad cm3 erg−1 were deduced for the nonvanishing components of the local cubic susceptibility tensor. For applied fields less than the saturation value, the sudden reduction of the thin film demagnetizing field leads to an imbalance of the torques acting upon ...

Conventional giant magnetoresistance (GMR) in spin valves is current-independent, so the resistance of a device depends only on the relative orientation of the magnetic layers. In dual spin valves consisting of three ferromagnetic (FM) layers separated by nonmagnetic (NM) spacers (i.e., a FM1/NM/FM2/NM/FM1), GMR can be current-dependent if spin can accumulate in FM2 when outer FM1 layers are aligned antiparallel. Currently the underlying physics is poorly understood, although spin accumulation in FM2 is likely to depend on the gradient in the density of states at the Fermi energy of the ferromagnet. To investigate this hypothesis, we have measured a series of dual spin valves with Ni1-xFex as FM2 layers of varying composition. We show that both the magnitude and sign of the nonlinear GMR depend strongly on the Fe content and thus on the band structure of the ferromagnet FM2.

We have used a transmission line deposited on a transparent substrate to deliver an optically triggered magnetic field pulse to a spin valve structure deposited upon an opaque substrate. The ensuing ferromagnetic resonance oscillations have been studied in optical pump-probe experiments in which the probe passes through the transmission line substrate. The resonance frequencies have been modeled by solving the Landau–Lifshitz equation and are used in determining the anisotropy, exchange bias, and interlayer coupling parameters of the sample.

A detailed investigation of magnetic impurity-mediated interlayer exchange coupling observed in Cu 0.94 Mn 0.06 / Co multilayers using polarized neutron reflectometry and magnetic x-ray techniques is reported. Excellent descriptions of temperature and magnetic field dependent biquadratic coupling are obtained using a variant of the loose spin model that takes into account the distribution of the impurity Mn ions in three dimensions. Positional disorder of the magnetic impurities is shown to enhance biquadratic coupling via a new contribution J fluct 2 , leading to a temperature dependent canting of magnetic domains in the multilayer. These results provide measurable effects on RKKY coupling associated with the distribution of impurities within planes parallel to the interfaces.

The recent discovery of nonlinear current-dependent magnetoresistance in dual spin valve devices [A. Aziz, O. P. Wessely, M. Ali, D. M. Edwards, C. H. Marrows, B. J. Hickey, and M. G. Blamire, Phys. Rev. Lett. 103, 237203 (2009)] opens up the possibility for distinct physics which extends the standard model of giant magnetoresistance. When the outer ferromagnetic layers of a dual spin valve are antiparallel, the resulting accumulation of spin in the middle ferromagnetic layer strongly modifies its bulk and interfacial spin asymmetry and resistance. Here, we report experimental evidence of the role of bulk spin accumulation in this nonlinear effect and show that interfacial spin accumulation alone cannot account for the observed dependence of the effect on the thickness of the middle ferromagnetic layer. It is also shown that spin torque acting on the middle ferromagnetic layer combined with the nonlinear effect might be useful in understanding the dynamical features associated with the nonlinear behavior.

Using the surface, interface, and element specificity of x-ray resonant magnetic scattering in combination with x-ray magnetic circular dichroism, we have spatially resolved the magnetic spin polarization, and the associated interface proximity effect, in a Mn-based high-susceptibility material close to a ferromagnetic Co layer. We have measured the magnetic polarization of Mn and Cu 3d electrons in paramagnetic CuMn alloy layers in [Co/Cu(x)/CuMn/Cu(x)](20) multilayer samples with varying copper layer thicknesses from x=0 to 25 angstrom. The size of the Mn and Cu L-2,L-3 edge dichroism shows a decrease in the Mn-induced polarization for increasing copper thickness indicating the dominant interfacial nature of the Cu and Mn spin polarization. The Mn polarization is much higher than that of Cu. Evidently, the Mn moment is a useful probe of the local spin density. Mn atoms appear to be coupled antiferromagnetically with the Co layer below x=10 angstrom and ferromagnetically coupled above. In contrast, the interfacial Cu atoms remain ferromagnetically aligned to the Co layer for all thicknesses studied.

The nanoscale magnetic structure of FeRh epilayers has been studied by polarized neutron reflectometry. Epitaxial films with a nominal thickness of 500 angstrom were grown on MgO (001) substrates via molecular-beam epitaxy and capped with 20 angstrom of MgO. The FeRh films show a clear transition from the antiferromagnetic (AF) state to the ferromagnetic (FM) state with increasing temperature. Surprisingly the films possess a FM moment even at a temperature 80 K below the AF-FM transition temperature of the film. We have quantified the magnitude and spatial extent of this FM moment, which is confined to within similar to 60-80 angstrom of the FeRh near the top and bottom interfaces. These interfacial FM layers account for the unusual effects previously observed in films with thickness

Standing spin waves in a thin film are used as sensitive probes of interface pinning induced by an antiferromagnet through exchange anisotropy. Using coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin wave thickness mode in Ni(80)Fe(20)/Ir(25)Mn(75) exchange biased bilayers was studied for a range of IrMn thicknesses. We show that pinning of the standing mode can be used to amplify, relative to the fundamental resonance, frequency shifts associated with exchange bias. The shifts provide a unique `fingerprint' of the exchange bias and can be interpreted in terms of an effective ferromagnetic film thickness and ferromagnet/antiferromagnet interface anisotropy. Thermal effects are studied for ultra-thin antiferromagnetic Ir(25)Mn(75) thicknesses, and the onset of bias is correlated with changes in the pinning fields. The pinning strength magnitude is found to grow with cooling of the sample, while the effective ferromagnetic film thickness simultaneously decreases. These results suggest that exchange bias involves some deformation of magnetic order in the interface region., Comment: 7 pages, 7 figures

Giant magnetoresistance (GMR) arises from differential scattering of the majority and minority spin electrons by a ferromagnet (FM) so that the resistance of a heterostructure depends on the relative magnetic orientation of the FM layers within it separated by nonmagnetic spacers. Here, we show that highly nonequilibrium spin accumulation in metallic heterostructures results in a current-dependent nonlinear GMR which is not predicted within the present understanding of GMR. The behavior can be explained by allowing the scattering asymmetries in an ultrathin FM layer to be current dependent.

Using a three-dimensional focused-ion beam lithography process we have fabricated nanopillar devices which show spin transfer torque switching at zero external magnetic fields. Under a small in-plane external bias field, a field-dependent peak in the differential resistance versus current is observed similar to that reported in asymmetrical nanopillar devices. This is interpreted as evidence for the low-field excitation of spin waves which in our case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange bias layer coupled to a relatively thin CoFe fixed layer., 11 pages, 4 figures. To appear in APL, April 2008

The effects of inserting impurity $\ensuremath{\delta}$ layers of various elements into a $\mathrm{Co}∕\mathrm{Ir}\mathrm{Mn}$ exchange biased bilayer, both at the interface and at given points within the IrMn layer a distance from the interface, have been investigated. Depending on the chemical species of impurity, and its position, we found that the exchange biasing can be either strongly enhanced or suppressed. We show that biasing is enhanced with a dusting of certain magnetic impurities, present either at the interface or sufficiently far away from the $\mathrm{Co}∕\mathrm{Ir}\mathrm{Mn}$ interface. This illustrates that the final spin structure at the $\mathrm{Co}∕\mathrm{Ir}\mathrm{Mn}$ interface is not only governed by interface structure and/or roughness, but is also mediated by local exchange or anisotropy variations within the bulk of the IrMn.

Optical pump-probe measurements of transient reflectivity were made on a sputtered polycrystalline thin film of hcp Zr. On top of a slow multiexponential decay, an oscillatory signal was observed with frequency varying from the initial value of ${f}_{0}=2.24\ifmmode\pm\else\textpm\fi{}0.06\phantom{\rule{0.3em}{0ex}}\mathrm{THz}$ at zero time delay to a value of $2.56\ifmmode\pm\else\textpm\fi{}0.12\phantom{\rule{0.3em}{0ex}}\mathrm{THz}$ after $2\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$, which is similar to that of a transverse optical (TO) phonon near the $\ensuremath{\Gamma}$ point of the Brillouin zone. From the data, the TO phonon relaxation time was determined to be $0.67\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$. The excitation of the coherent phonon was identified as being mediated by resonant coherent Raman scattering.

Time-resolved ellipsometric measurements were made upon Au, Cu, Ag, Ni, Pd, Ti, Zr, and Hf thin films. Using an elliptically polarized pump beam, the decay of the optically induced polarization of the sample was observed. Characteristic relaxation times are extracted and interpreted in terms of scattering of linear and angular momentum of hot electrons. A systematic variation is observed between different metals that reflects their underlying band structure.

Broadband ferromagnetic resonance responses for metallic single-layer and bilayer magnetic films with total thicknesses smaller than the microwave magnetic skin depth have been studied. Two different types of microwave stripline transducers were used to excite and detect magnetization precession: a coplanar waveguide and a microstrip line both with characteristic width larger than the free propagation path for traveling spin waves along the film. Both transducers show efficient excitation of higher-order standing spin wave modes across the film thickness in samples 30–91 nm thick. The ratio of amplitudes of the first standing spin wave to the fundamental resonant mode is independent of frequency for single-layer permalloy films. In contrast, we find a strong variation in the amplitudes with frequency for cobalt–Permalloy bilayers and the ratio is strongly dependent on the ordering of layers with respect to a stripline transducer. Most importantly, cavity ferromagnetic resonance measurements on the same samples show considerably weaker amplitudes for the standing spin waves. All experimental data are consistent with expected effects of eddy currents in films with thicknesses below the microwave magnetic skin depth. Finally, conditions for observing eddy current effects in different types of experiments are critically examined.