We investigate the role of lithographically-induced strain relaxation in a micron-scaled device fabricated from epitaxial thin films of the magnetostrictive alloy Fe
Ga
. The strain relaxation due to ...lithographic patterning induces a magnetic anisotropy that competes with the magnetocrystalline and shape induced anisotropies to play a crucial role in stabilising a flux-closing domain pattern. We use magnetic imaging, micromagnetic calculations and linear elastic modelling to investigate a region close to the edges of an etched structure. This highly-strained edge region has a significant influence on the magnetic domain configuration due to an induced magnetic anisotropy resulting from the inverse magnetostriction effect. We investigate the competition between the strain-induced and shape-induced anisotropy energies, and the resultant stable domain configurations, as the width of the bar is reduced to the nanoscale range. Understanding this behaviour will be important when designing hybrid magneto-electric spintronic devices based on highly magnetostrictive materials.
Here we present a magnetic thin film with a weak ferrimagnetic (FIM) phase above the Néel temperature (\(T_{N}\) = 240 K) and a non-collinear antiferromagnetic (AFM) phase below, exhibiting a small ...net magnetisation due to strain-associated canting of the magnetic moments. A long-range ordered FIM phase has been predicted in related materials, but without symmetry analysis. We now perform this analysis and use it to calculate the MOKE spectra in AFM and FIM phases. From the good agreement between the form of the measured and predicted MOKE spectra, we propose the AFM and FIM phases share the magnetic space group C2'/m' and that the symmetry driven magneto-optic and magneto-transport properties are maximised at room temperature in the FIM phase due to the non-zero intrinsic Berry phase contribution present in these materials. A room temperature FIM phase with large optical and transport signatures, as well as sensitivity to lattice strain and magnetic field, has useful prospects for high-speed spintronic applications.
The intrinsic anomalous Nernst effect in a magnetic material is governed by the Berry curvature at the Fermi energy and can be realized in non-collinear antiferromagnets with vanishing magnetization. ...Thin films of (001)-oriented Mn\(_{3}\)NiN have their chiral antiferromagnetic structure located in the (111) plane facilitating the anomalous Nernst effect unusually in two orthogonal in-plane directions. The sign of each component of the anomalous Nernst effect is determined by the local antiferromagnetic domain state. In this work, a temperature gradient is induced in a 50 nm thick Mn\(_{3}\)NiN two micron-size Hall cross by a focused scanning laser beam, and the spatial distribution of the anomalous Nernst voltage is used to image and identify the octupole macrodomain arrangement. Although the focused laser beam width may span many individual domains, cooling from room temperature through the antiferromagnetic transition temperature in an in-plane magnetic field prepares the domain state producing a checkerboard pattern resulting from the convolution of contributions from each domain. These images together with atomistic and micromagnetic simulations suggest an average macrodomain of the order of \(1 {\mu}m^{2}\).
Spin-dependent transport phenomena due to relativistic spin-orbit coupling and broken space-inversion symmetry are often difficult to interpret microscopically, in particular when occurring at ...surfaces or interfaces. Here we present a theoretical and experimental study of spin-orbit torque and unidirectional magnetoresistance in a model room-temperature ferromagnet NiMnSb with inversion asymmetry in the bulk of this half-heusler crystal. Besides the angular dependence on magnetization, the competition of Rashba and Dresselhaus-like spin-orbit couplings results in the dependence of these effects on the crystal direction of the applied electric field. The phenomenology that we observe highlights potential inapplicability of commonly considered approaches for interpreting experiments. We point out that, in general, there is no direct link between the current-induced non-equilibrium spin polarization inferred from the measured spin-orbit torque and the unidirectional magnetiresistance. We also emphasize that the unidirectional magnetoresistance has not only longitudinal but also transverse components in the electric field -- current indices which complicates its separation from the thermoelectric contributions to the detected signals in common experimental techniques. We use the theoretical results to analyze our measurements of the on-resonance and off-resonance mixing signals in microbar devices fabricated from an epitaxial NiMnSb film along different crystal directions. Based on the analysis we extract an experimental estimate of the unidirectional magnetoresistance in NiMnSb.
Transport calculations based on ab-initio band structures reveal large interface-generated spin currents at Co/Pt, Co/Cu, and Pt/Cu interfaces. These spin currents are driven by in-plane electric ...fields but flow out-of-plane, and can have similar strengths to spin currents generated by the spin Hall effect in bulk Pt. Each interface generates spin currents with polarization along \(\bf{\hat{z}} \times \bf{E}\), where \(\bf{\hat{z}}\) is the interface normal and \(\bf{E}\) denotes the electric field. The Co/Cu and Co/Pt interfaces additionally generate spin currents with polarization along \(\bf{\hat{m}} \times (\bf{\hat{z}} \times \bf{E})\), where \(\bf{\hat{m}}\) gives the magnetization direction of Co. The latter spin polarization is controlled by---but not aligned with---the magnetization, providing a novel mechanism for generating spin torques in magnetic trilayers.
The aim of this study was to characterize the spectrum of β-glucocerebrosidase gene mutations in Czech and Slovak Gaucher patients and to study genotype/phenotype associations. We have analyzed ...fifty-eight chromosomes from twenty-six type 1, two type 2, and one type 3 β-glucocerebrosidase deficient subjects by direct sequencing of PCR products. Fifty-eight mutant alleles were identified.
Seventy-eight percent of mutant alleles carried common mutations (N370S 28/58, L444P 11/58, recNciI 5/58, and IVS2(+1)A 1/58), the remaining twenty-two percent carried rare and private mutations (1263del55, 1326insT, S196P, rec(g4889–6506), 203delC, G202E, F216Y, R257X, R120W, R359Q, S107L, L444P + V460V, and D409H + T369M). Six of these alleles have not been previously described (rec(g4889–6506), 1326insT, S196P, G202E, D409H + T369M, and L444P + V460V). The most common genotypes were N370S/L444P (8/29), N370S/recNciI (5/29), and N370S/N370S (2/29).
The spectrum of the mutations is characteristic for a Caucasian (non-Jewish) population, with N370S, L444P and recNciI being the most prevalent mutations. The absence of the mutation 84insG that is frequently associated with severe bone disease may have contributed to the low incidence of severe bone disease in Czech and Slovak Gaucher subjects.
Phys. Rev. B 95, 184438 (2017) We model changes of magnetic ordering in Mn-antiperovskite nitrides driven by
biaxial lattice strain at zero and at finite temperature. We employ a
non-collinear ...spin-polarised density functional theory to compare the response
of the geometrically frustrated exchange interactions to a tetragonal symmetry
breaking (the so called piezomagnetic effect) across a range of Mn$_3$AN (A =
Rh, Pd, Ag, Co, Ni, Zn, Ga, In, Sn) at zero temperature. Building on the
robustness of the effect we focus on Mn$_3$GaN and extend our study to finite
temperature using the disordered local moment (DLM) first-principles electronic
structure theory to model the interplay between the ordering of Mn magnetic
moments and itinerant electron states. We discover a rich temperature-strain
magnetic phase diagram with two previously unreported phases stabilised by
strains larger than 0.75\% and with transition temperatures strongly dependent
on strain. We propose an elastocaloric cooling cycle crossing two of the
available phase transitions to achieve simultaneously a large isothermal
entropy change (due to the first order transition) and a large adiabatic
temperature change (due to the second order transition).
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