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Multielement rare earth (R)–transition metal (T) intermetallics are arguably the next generation of high-performance permanent magnetic materials for future applications in energy-saving and renewable energy technologies. Pseudobinary Sm2Fe17N3 and (R,Zr)(Fe,Co,Ti)12 (R = Nd, Sm) compounds have the highest potential to meet current demands for rare-earth-element-lean permanent magnets (PMs) with ultra-large energy product and operating temperatures up to 200°C. However, the synthesis of these materials, especially in the mesoscopic scale for maximizing the maximum energy product ($${\left({BH} \right)_{{\rm{max}}}}$$), remains a great challenge. Nonequilibrium processes are apparently used to overcome the phase-stabilization challenge in preparing the R–T intermetallics but have limited control of the material’s microstructure. More radical bottom-up nanoparticle approaches based on chemical synthesis have also been explored, owing to their potential to achieve the desired composition, structure, size, and shape. While a great achievement has been made for the Sm2Fe17N3, progress in the synthesis of (R,Zr)(Fe,Co,Ti)12 magnetic mesoscopic particles (MMPs) and R–T/T exchange-coupled nanocomposites (NCMs) with substantial coercivity ($${H_{\rm{c}}}$$) and remanence ($${M_{\rm{r}}})$$, respectively, remains marginal.

The interplay between charges and spins may influence the dynamics of the carriers and determine their thermoelectric properties. In that respect, magneto-thermoelectric power MTEP, i.e. the measurements of the Seebeck coefficient S under the application of an external magnetic field, is a powerful technique to reveal the role of magnetic moments on S. This is illustrated by different transition metal chalcogenides: CuCrTiS4 and CuMnTiS4 magnetic thiospinels, which are compared with magnetic oxides, Curie-Weiss (CW) paramagnetic misfit cobaltites, ruthenates, either ferromagnetic perovskite or Pauli paramagnet quadruple perovskites, and CuGa1-xMnxTe2 chalcopyrite telluride and Bi1.99Cr0.01Te3 in which diluted magnetism is induced by 3%-Mn and 1%-Cr substitution, respectively. In the case of a ferromagnet (below TC) and CW paramagnetic materials, the increase of magnetization at low T when a magnetic field is applied is accompanied by a decrease of the entropy of the carriers and hence S decreases. This is consistent with the lack of MTEP in the Pauli paramagnetic quadruple perovskites. Also, no significant MTEP is observed in CuGa1-xMnxTe2 and Bi1.99Cr0.01Te3, for which Kondo-type interaction between magnetic moments and carriers prevails. In contrast, spin glass CuCrTiS4 exhibits negative MTEP like in ferromagnetic ruthenates and paramagnetic misfit cobaltites. This investigation of some chalcogenides and oxides provides key ingredients to select magnetic materials for which S benefits from spin entropy. [ABSTRACT FROM AUTHOR]

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB2. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho1-xDyxB2 alloys (x = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature (TC) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |ΔSM| and adiabatic temperature change ΔTad showed a gradual decrease. On the other hand, due to the presence of successive transitions in these alloys, the peak height of the above magnetocaloric properties tends to be kept in a wide temperature range, leading to a relatively robust figure of merit in a wide temperature span. These alloys could be interesting candidates for magnetic refrigeration in the temperature range of 10–60 K. [ABSTRACT FROM AUTHOR]

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB2. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho1-xDyxB2 alloys (x = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature (TC) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |ΔSM| and adiabatic temperature change ΔTad showed a gradual decrease. On the other hand, due to the presence of successive transitions in these alloys, the peak height of the above magnetocaloric properties tends to be kept in a wide temperature range, leading to a relatively robust figure of merit in a wide temperature span. These alloys could be interesting candidates for magnetic refrigeration in the temperature range of 10–60 K. [ABSTRACT FROM AUTHOR]

We have developed hard X-ray photoelectron spectroscopy (HAXPES) under an applied magnetic field of 1 kOe to study the electronic and magnetic states related to the MgO/Fe interface-induced perpendicular magnetic anisotropy (PMA). In this work, we used MgO (2 nm)/Fe (1.5 and 20 nm)/MgO(001) structures to reveal the interface-induced electronic states of the Fe film. Perpendicular magnetization of the 1.5-nm-thick Fe film without extrinsic oxidation of the Fe film was detected by the Fe 2p core-level magnetic circular dichroism (MCD) in HAXPES under a magnetic field, and easy magnetization axis perpendicular to the film plane was confirmed by ex situ magnetic hysteresis measurements. The valence-band HAXPES spectrum of the 1.5-nm-thick Fe film revealed that the Fe 3d electronic states were strongly modified from the thick Fe film and a reference bulk Fe sample due to the lifting of degeneracy in the Fe 3d states near the MgO/Fe interface. We found that the tetragonal distortion of the Fe film by the MgO substrate also contributes to the lifting of degeneracy in the Fe 3d states and PMA, as well as the Fe 3d-O 2p hybridization at the MgO/Fe interface, by comparing the valence-band spectrum with density functional theory calculations for MgO/Fe multilayer structures. Thus, we can conclude that the Fe 3d-O 2p hybridization and tetragonal distortion of the Fe film play important roles in PMA at the MgO/Fe interface. HAXPES with in situ magnetization thus represents a powerful new method for studying spintronic structures. [ABSTRACT FROM AUTHOR]

The anomalous Nernst effect (ANE), one of the thermomagnetic effects studied for a long time, has recently attracted renewed attention. The ANE, which originates from fictitious fields in momentum space, is essential for clarifying the interplay among heat, spin, and charge in magnets. Moreover, compared to the Seebeck effect, it has various benefits for application to high-efficiency energy-harvesting devices as it may provide much more simple lateral structure, higher flexibility, and much lower production cost. In this review, we discuss various topics related to the methods to modulate the ANE for its thermoelectric applications. In addition, we review strategies to design materials to obtain large ANE including Weyl magnets and thermoelectric devices for effectively utilizing the ANE. [ABSTRACT FROM AUTHOR]

In this review we describe recent advances in transition metal oxyhydride chemistry obtained by topochemical routes, such as low temperature reduction with metal hydrides, or high-pressure solid-state reactions. Besides the crystal chemistry, magnetic and transport properties of the bulk powder and epitaxial thin film samples, the remarkable lability of the hydride anion is particularly highlighted as a new strategy to discover unprecedented mixed anion materials. [ABSTRACT FROM AUTHOR]

The electronic transport properties of the delafossite oxidesare usually understood in terms of two well-separated entities, namely the triangularand (layers. Here, we review several cases among this extensive family of materials where the transport depends on the interlayer coupling and displays unconventional properties. We review the doped thermoelectrics based onand, which show a high-temperature recovery of Fermi-liquid transport exponents, as well as the highly anisotropic metals,, and, where the sheer simplicity of the Fermi surface leads to unconventional transport. We present some of the theoretical tools that have been used to investigate these transport properties and review what can and cannot be learned from the extensive set of electronic structure calculations that have been performed. [ABSTRACT FROM AUTHOR]

We propose a novel representation of materials named an ‘orbital-field matrix (OFM)’, which is based on the distribution of valence shell electrons. We demonstrate that this new representation can be highly useful in mining material data. Experimental investigation shows that the formation energies of crystalline materials, atomization energies of molecular materials, and local magnetic moments of the constituent atoms in bimetal alloys of lanthanide metal and transition-metal can be predicted with high accuracy using the OFM. Knowledge regarding the role of the coordination numbers of the transition-metal and lanthanide elements in determining the local magnetic moments of the transition-metal sites can be acquired directly from decision tree regression analyses using the OFM. [ABSTRACT FROM AUTHOR]

Thin (4–20 nm) yttrium iron garnet (Y3Fe5O12, YIG) layers have been grown on gadolinium gallium garnet (Gd3Ga5O12, GGG) 111-oriented substrates by laser molecular beam epitaxy in 700–1000 °C growth temperature range. The layers were found to have atomically flat step-and-terrace surface morphology with step height of 1.8 Å characteristic for YIG(111) surface. As the growth temperature is increased from 700 to 1000 °C the terraces become wider and the growth gradually changes from layer by layer to step-flow regime. Crystal structure studied by electron and X-ray diffraction showed that YIG lattice is co-oriented and laterally pseudomorphic to GGG with small rhombohedral distortion present perpendicular to the surface. Measurements of magnetic moment, magneto-optical polar and longitudinal Kerr effect (MOKE), and X-ray magnetic circular dichroism (XMCD) were used for study of magnetization reversal for different orientations of magnetic field. These methods and ferromagnetic resonance studies have shown that in zero magnetic field magnetization lies in the film plane due to both shape and induced anisotropies. Vectorial MOKE studies have revealed the presence of an in-plane easy magnetization axis. In-plane magnetization reversal was shown to occur through combination of reversible rotation and abrupt irreversible magnetization jump, the latter caused by domain wall nucleation and propagation. The field at which the flip takes place depends on the angle between the applied magnetic field and the easy magnetization axis and can be described by the modified Stoner–Wohlfarth model taking into account magnetic field dependence of the domain wall energy. Magnetization curves of individual tetrahedral and octahedral magnetic Fe3+sublattices were studied by XMCD. [ABSTRACT FROM AUTHOR]

Thin film libraries of Fe-Co-V were fabricated by combinatorial sputtering to study magnetic and structural properties over wide ranges of composition and thickness by high-throughput methods: synchrotron X-ray diffraction, magnetometry, composition, and thickness were measured across the Fe-Co-V libraries. In-plane magnetic hysteresis loops were shown to have a coercive field of 23.9 kA m–1(300 G) and magnetization of 1000 kA m–1. The out-of-plane direction revealed enhanced coercive fields of 207 kA m–1(2.6 kG) which was attributed to the shape anisotropy of column grains observed with electron microscopy. Angular dependence of the switching field showed that the magnetization reversal mechanism is governed by 180° domain wall pinning. In the thickness-dependent combinatorial study, co-sputtered composition spreads had a thickness ranging from 50 to 500 nm and (Fe70Co30)100-xVxcompositions of x = 2–80. Comparison of high-throughput magneto-optical Kerr effect and traditional vibrating sample magnetometer measurements show agreement of trends in coercive fields across large composition and thickness regions. [ABSTRACT FROM AUTHOR]

Au–FexOycomposite nanoparticles (NPs) are of great technological interest due to their combined optical and magnetic properties. However, typical syntheses are neither simple nor ecologically friendly, creating a challenging situation for process scale-up. Here we describe conditions for preparing Au–FexOyNPs in aqueous solutions and at ambient temperatures, without resorting to solvents or amphiphilic surfactants with poor sustainability profiles. These magnetic gold nanoclusters (MGNCs) are prepared in practical yields with average sizes slightly below 100 nm, and surface plasmon resonances that extend to near-infrared wavelengths, and sufficient magnetic moment (up to 6 emu g–1) to permit collection within minutes by handheld magnets. The MGNCs also produce significant photoluminescence when excited at 488 nm. Energy dispersive X-ray (EDX) analysis indicates a relatively even distribution of Fe within the MGNCs, as opposed to a central magnetic core. [ABSTRACT FROM AUTHOR]

A CVD-grown boron-doped diamond film was polished to a surface roughness of2 nm RMS. The superconducting properties of the film are unchanged by the polishing process. Chemical vapour deposition (CVD) grown boron-doped nanocrystalline diamond (B-NCD) is an attractive material for the fabrication of high frequency superconducting nanoelectromechanical systems (NEMS) due to its high Young’s modulus. The as-grown films have a surface roughness that increases with film thickness due to the columnar growth mechanism. To reduce intrinsic losses in B-NCD NEMS it is crucial to correct for this surface roughness by polishing. In this paper, in contrast to conventional polishing, it is demonstrated that the root-mean-square (RMS) roughness of a 520 nm thick B-NCD film can be reduced by chemical mechanical polishing (CMP) from 44.0 nm to 1.5 nm in 14 hours without damaging the sample or introducing significant changes to the superconducting transition temperature,, thus enabling the use of B-NCD films in the fabrication of high quality superconducting NEMS. [ABSTRACT FROM AUTHOR]

We present a study of the electrical and magnetic properties of the amorphousGe1-xMnx.DMS, with 2% ≤ x ≤ 17%, by means of SQUID magnetometry and low temperature DC measurements. The thin films were grown by physical vapour deposition at 50°C in ultrahigh vacuum. The DC electrical characterizations show that variable range hopping is the main mechanism of charge transport below room temperature. Magnetic characterization reveals that a unique and smooth magnetic transition is present in our samples, which can be attributed to ferromagnetic percolation of bound magnetic polarons. [ABSTRACT FROM AUTHOR]

Nanoscale magnetic materials are the basis of emerging technologies to develop novel magnetoelectronic devices. Self-assembly of polystyrene nanospheres is here used to generate 2D hexagonal dot arrays on Fe50Pd50thin films. This simple technique allows a wide-area patterning of a magnetic thin film. The role of disorder on functional magnetic properties with respect to conventional lithographic techniques is studied. Structural and magnetic characteristics have been investigated in arrays having different geometry (i.e. dot diameters, inter-dot distances and thickness). The interplay among microstructure and magnetization reversal is discussed. Magnetic measurements reveal a vortex domain configuration in all as-prepared films. The original domain structure changes drastically upon thermal annealing performed to promote the transformation of disordered A1 phase into the ordered, tetragonal L10phase. First-order reversal magnetization curves have been measured to rule out the role of magnetic interaction among crystalline phases characterized by different magnetic coercivity. [ABSTRACT FROM AUTHOR]

A facile synthetic approach to prepare porous ZnO@CuNi hybrid films is presented. Initially, magnetic CuNi porous layers (consisting of phase separated CuNi alloys) are successfully grown by electrodeposition at different current densities using H2bubbles as a dynamic template to generate the porosity. The porous CuNi alloys serve as parent scaffolds to be subsequently filled with a solution containing ZnO nanoparticles previously synthesized by sol-gel. The dispersed nanoparticles are deposited dropwise onto the CuNi frameworks and the solvent is left to evaporate while the nanoparticles impregnate the interior of the pores, rendering ZnO-coated CuNi 3D porous structures. No thermal annealing is required to obtain the porous films. The synthesized hybrid porous layers exhibit an interesting combination of tunable ferromagnetic and photoluminescent properties. In addition, the aqueous photocatalytic activity of the composite is studied under UV−visible light irradiation for the degradation of Rhodamine B. The proposed method represents a fast and inexpensive approach towards the implementation of devices based on metal-semiconductor porous systems, avoiding the use of post-synthesis heat treatment steps which could cause deleterious oxidation of the metallic counterpart, as well as collapse of the porous structure and loss of the ferromagnetic properties. [ABSTRACT FROM PUBLISHER]

We set out to demonstrate the development of a highly conductive polymer based on poly-(3,4-ethylenedithia thiophene) (PEDTT), PEDOTs structural analogue historically notorious for structural disorder and limited conductivities. The caveat therein was previously described to lie in intra-molecular repulsions. We demonstrate how a tremendous >2600-fold improvement in conductivity and metallic features, such as magnetoconductivity can be achieved. This is achieved through a careful choice of the counter-ion (sulphate) and the use of oxidative chemical vapour deposition (oCVD). It is shown that high structural order on the molecular level was established and the formation of crystallites tens of nanometres in size was achieved. We infer that the sulphate ions therein intercalate between the polymer chains, thus forming densely packed crystals of planar molecules with extended π-systems. Consequently, room-temperature conductivities of above 1000 S cm -1 are achieved, challenging those of conventional PEDOT:PSS. The material is in the critical regime of the metal-insulator transition., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

A thermomagnetic generator is a promising technology to harvest low-grade waste heat and convert it into electricity. To make this technology competitive with other technologies for energy harvesting near room temperature, the optimum thermomagnetic material is required. Here we compare the performance of a state of the art thermomagnetic generator using gadolinium and La-Fe-Co-Si as thermomagnetic material, which exhibit strong differences in thermal conductivity and type of magnetic transition. gadolinium is the established benchmark material for magnetocaloric cooling, which follows the reverse energy conversion process as compared to thermomagnetic energy harvesting. Surprisingly, La-Fe-Co-Si outperforms gadolinium in terms of voltage and power output. Our analysis reveals the differences in thermal conductivity are less important than the particular shape of the magnetization curve. In gadolinium an unsymmetrical magnetization curve is responsible for an uncompensated magnetic flux, which results in magnetic stray fields. These stray fields represent an energy barrier in the thermodynamic cycle and reduce the output of the generator. Our detailed experiments and simulations of both, thermomagnetic materials and generator, clearly reveal the importance to minimize magnetic stray fields. This is only possible when using materials with a symmetrical magnetization curve, such as La-Fe-Co-Si. [ABSTRACT FROM AUTHOR]

Permanent magnets, and particularly rare earth magnets such as Nd-Fe-B, have attracted much attention because of their magnetic properties. There are two well-established techniques for obtaining sintered magnets and bonded Nd-Fe-B magnets. Powder metallurgy is used to obtain high-performance anisotropic sintered magnets. To produce bonded magnets, either melt-spinning or the hydrogenation, disproportionation, desorption, and recombination process is used to produce magnet powders, which are then mixed with binders. Since the development of Nd-Fe-B magnets, several kinds of intermetallic compounds have been reported, such as Sm 2 Fe 17 N x and Sm(Fe,M) 12 (M: Ti, V, etc.). However, it is difficult to apply a liquid-phase sintering process similar to the one used for Nd-Fe-B sintered magnets in order to produce high-performance Sm-Fe-based sintered magnets because of the low decomposition temperature of the compound and the lack of a liquid grain boundary phase like that in the Nd-Fe-B system. Therefore, bonded magnets are useful in the production of bulk magnets using these Sm-Fe-based compounds. This article reviews recent progress in our work on the development of high-performance bonded magnets using Nd 2 Fe 14 B and Sm 2 Fe 17 N x compounds., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

First-principles calculation based on density functional theory is a powerful tool for understanding and designing magnetic materials. It enables us to quantitatively describe magnetic properties and structural stability, although further methodological developments for the treatment of strongly correlated 4f electrons and finite-temperature magnetism are needed. Here, we review recent developments of computational schemes for rare-earth magnet compounds, and summarize our theoretical studies on Nd 2 Fe 14 B and R Fe 12 -type compounds. Effects of chemical substitution and interstitial dopants are clarified. We also discuss how data-driven approaches are used for studying multinary systems. Chemical composition can be optimized with fewer trials by the Bayesian optimization. We also present a data-assimilation method for predicting finite-temperature magnetization in wide composition space by integrating computational and experimental data., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

For any thermoelectric effects to be achieved, a thermoelectric material must have hot and cold sides. Typically, the hot side can be easily obtained by excess heat. However, the passive cooling method is often limited to convective heat transfer to the surroundings. Since thermoelectric voltage is proportional to the temperature difference between the hot and cold sides, efficient passive cooling to increase the temperature gradient is of critical importance. Here, we report simultaneous harvesting of radiative cooling at the top and solar heating at the bottom to enhance the temperature gradient for a transverse thermoelectric effect which generates thermoelectric voltage perpendicular to the temperature gradient. We demonstrate this concept by using the spin Seebeck effect and confirm that the spin Seebeck device shows the highest thermoelectric voltage when both radiative cooling and solar heating are utilized. Furthermore, the device generates thermoelectric voltage even at night through radiative cooling which enables continuous energy harvesting throughout a day. Planar geometry and scalable fabrication process are advantageous for energy harvesting applications., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

To realize a sustainable society, 'green technology' with low (or even zero) CO 2 emissions is required. A key material in such technology is a permanent magnet because it is utilized for electric-power conversion in several applications including electric vehicles (EVs), hybrid EVs (HEVs), and turbines for wind power generation. To realize highly efficient electric-power conversion, a stronger permanent magnet than Nd-Fe-B is necessary. One potential candidate is a Fe-rich SmFe 12 -based compound with a ThMn 12 structure. In this paper, the phase stability, structure, and intrinsic and extrinsic magnetic properties in both film and bulk forms are reviewed. Based on these results, a possible way to realize a strong SmFe 12 -based permanent magnet in bulk form is discussed., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Physically, the coercivity of permanent magnets should scale with the anisotropy field of ferromagnetic compounds, H A ; however, the typical coercivity values of commercial polycrystalline sintered magnets are only ~0.2  H A , which is known as Brown's paradox. Recent advances in multi-scale microstructure characterizations using focused ion beam scanning electron microscope (FIB/SEM), aberration corrected scanning transmission electron microscopy (C s -corrected STEM), and atom probe tomography (APT) revealed detailed microstructural features of commercial and experimental Nd-Fe-B magnets. These investigations suggest the magnetism of a thin layer formed along grain boundaries (intergranular phase) is a critical factor that influences the coercivity of polycrystalline magnets. To determine the magnetism of the thin intergranular phase, soft X-ray magnetic circular dichroism and electron holography play critical roles. Large-scale micromagnetic simulations using the models that are close to real microstructure incorporating the recent microstructure characterization results gave insights on how the coercivity and its thermal stability is influenced by the microstructures. Based on these new findings, coercivity of Nd-Fe-B magnets is being improved to its limit. This review replies to the most frequently asked questions about the coercivity of Nd-Fe-B permanent magnets based on our recent studies., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

For the Nd-Fe-B permanent magnets, a prototype thermodynamic database of the 8-element system (Nd, Fe, B, Al, Co, Cu, Dy, Ga) was constructed based on literature data and assessed parameters in the present work. The magnetic excess Gibbs energy of the Nd 2 Fe 14 B compound was reassessed using thoroughly measured heat capacity data. The Dy-Nd binary system was reassessed based on formation energies estimated from ab initio calculations. The constructed database was applied successfully for estimations of phase equilibria during the grain boundary diffusion processes (GBDP) and the reactions in the hydrogenation decomposition desorption recombination (HDDR) processes., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Development of high-performance permanent magnets relies on both the main-phase compound with superior intrinsic magnetic properties and the microstructure effect for the prevention of magnetization reversal. In this article, the microstructure effect is discussed by focusing on the interface between the main phase and an intergranular phase and on the intergranular phase itself. First, surfaces of main-phase grains are considered, where a general trend in the surface termination and its origin are discussed. Next, microstructure interfaces in SmFe 12 -based magnets are discussed, where magnetic decoupling between SmFe 12 grains is found for the SmCu subphase. Finally, general insights into finite-temperature magnetism are discussed with emphasis on the feedback effect from magnetism-dependent phonons on magnetism, which is followed by explanations on atomic arrangements and magnetism of intergranular phases in Nd-Fe-B magnets. Both amorphous and candidate crystalline structures of Nd-Fe alloys are considered. The addition of Cu and Ga to Nd-Fe alloys is demonstrated to be effective in decreasing the Curie temperature of the intergranular phase., Competing Interests: No potential conflict of interest was reported by the author., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

In the present paper we discuss correlations between crystal structure and magnetic properties of epitaxial ε-Fe 2 O 3 films grown on GaN. The large magnetocrystalline anisotropy and room temperature multiferroic properties of this exotic iron oxide polymorph, make it a perspective material for the development of low power consumption magnetic media storage devices. Extending our recent progress in PLD growth of ε-Fe 2 O 3 on the surface of technologically important nitride semiconductors, we apply reciprocal space tomography by electron and x-ray diffraction to investigate the break of crystallographic symmetry occurring at the oxide-nitride interface resulting in the appearance of anisotropic crystallographic disorder in the sub-100 nm ε-Fe 2 O 3 films. The orthorhombic-on-hexagonal nucleation scenario is shown responsible for the development of a peculiar columnar structure observed in ε-Fe 2 O 3 by means of HRTEM and AFM. The complementary information on the direct and reciprocal space structure of the columnar ε-Fe 2 O 3 films is obtained by various techniques and correlated to their magnetic properties. The peculiar temperature dependence of magnetization studied by the small-field magnetization derivative method and by neutron diffraction reveals the existence of a magnetic softening below 150 K, similar to the one observed earlier solely in nanoparticles. The magnetization reversal in ε-Fe 2 O 3 films probed by X-ray magnetic circular dichroism is found different from the behavior of the bulk averaged magnetization measured by conventional magnetometry. The presented results fill the gap between the numerous studies performed on randomly oriented ε-Fe 2 O 3 nanoparticles and much less frequent investigations of epitaxial epsilon ferrite films with lattice orientation fixed by the substrate., Competing Interests: The authors declare no conflict of interest., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB 2 . Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho 1- x Dy x B 2 alloys ( x = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature ( T C ) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |Δ S M | and adiabatic temperature change Δ T ad showed a gradual decrease. On the other hand, due to the presence of successive transitions in these alloys, the peak height of the above magnetocaloric properties tends to be kept in a wide temperature range, leading to a relatively robust figure of merit in a wide temperature span. These alloys could be interesting candidates for magnetic refrigeration in the temperature range of 10-60 K., Competing Interests: The authors declare no conflict of interest., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Multielement rare earth (R)-transition metal (T) intermetallics are arguably the next generation of high-performance permanent magnetic materials for future applications in energy-saving and renewable energy technologies. Pseudobinary Sm 2 Fe 17 N 3 and (R,Zr)(Fe,Co,Ti) 12 (R = Nd, Sm) compounds have the highest potential to meet current demands for rare-earth-element-lean permanent magnets (PMs) with ultra-large energy product and operating temperatures up to 200°C. However, the synthesis of these materials, especially in the mesoscopic scale for maximizing the maximum energy product ( B H m a x ), remains a great challenge. Nonequilibrium processes are apparently used to overcome the phase-stabilization challenge in preparing the R-T intermetallics but have limited control of the material's microstructure. More radical bottom-up nanoparticle approaches based on chemical synthesis have also been explored, owing to their potential to achieve the desired composition, structure, size, and shape. While a great achievement has been made for the Sm 2 Fe 17 N 3 , progress in the synthesis of (R,Zr)(Fe,Co,Ti) 12 magnetic mesoscopic particles (MMPs) and R-T/T exchange-coupled nanocomposites (NCMs) with substantial coercivity ( H c ) and remanence ( M r ) , respectively, remains marginal., Competing Interests: No potential conflict of interest was reported by the authors., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)