Tunneling magnetoresistance in ensembles of ferromagnetic granules with exchange interaction and random easy axes of magnetic anisotropy

Observation of Large Unidirectional Rashba Magnetoresistance in Ge(111)

Relating magnetotransport properties to specific spin textures at surfaces or interfaces is an intense field of research nowadays. Here, we investigate the variation of the electrical resistance of Ge(111) grown epitaxially on semi-insulating Si(111) under the application of an external magnetic field. We find a magnetoresistance term which is linear in current density j and magnetic field B, hence odd in j and B, corresponding to a unidirectional magnetoresistance. At 15 K, for I = 10 $μ$A (or j = 0.33 A/m) and B = 1 T, it represents 0.5 % of the zero field resistance, a much higher value com…

Theory of bilinear magneto-electric resistance from topological-insulator surface states

We theoretically investigate a new kind of nonlinear magnetoresistance on the surface of three-dimensional topological insulators (TIs). At variance with the unidirectional magnetoresistance (UMR) effect in magnetic bilayers, this nonlinear magnetoresistance does not rely on a conducting ferromagnetic layer and scales linearly with both the applied electric and magnetic fields; for this reason, we name it bilinear magneto-electric resistance (BMER). We show that the sign and the magnitude of the BMER depends sensitively on the orientation of the current with respect to the magnetic field as we…

Positive magnetoresistance and chiral anomaly in exfoliated type-II Weyl semimetal $T_\mathrm{d}$-WTe$_{2}$

Layered van der Waals semimetallic $T_\mathrm{d}$-WTe$_{2}$, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as model topological type-II Weyl semimetal system. Here, $\sim$45 nm thick mechanically exfoliated flakes of $T_\mathrm{d}$-WTe$_{2}$ are studied $via$ atomic force microscopy, Raman spectroscopy, low-$T$/high-$μ_{0}H$ magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse $\mathrm{MR}_\per…

Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe

A common perception assumes that magnetic memories require ferromagnetic materials with a non-zero net magnetic moment. However, it has been recently proposed that compensated antiferromagnets with a zero net moment may represent a viable alternative to ferromagnets. So far, experimental research has focused on bistable memories in antiferromagnetic metals. In the present work we demonstrate a multiple-stable memory device in epitaxial manganese telluride (MnTe) which is an antiferromagnetic counterpart of common II-VI semiconductors. Favorable micromagnetic characteristics of MnTe allow us to…

d波交替磁体KV₂Se₂O中固有自旋滤波效应

Intrinsic Spin Filter Effect in a $d$-wave altermagnet KV$_2$Se$_2$O with Open Fermi Surface

d波交替磁体KV₂Se₂O通过方向依赖的自旋过滤实现高隧道磁电阻，展示出稳定的半金属传输和室温下的自旋Seebeck效应。

Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities

Anisotropic magnetoresistance (AMR) is a relativistic magnetotransport phenomenon arising from combined effects of spin-orbit coupling and broken symmetry of a ferromagnetically ordered state of the system. In this work we focus on one realization of the AMR in which spin-orbit coupling enters via specific spin-textures on the carrier Fermi surfaces and ferromagnetism via elastic scattering of carriers from polarized magnetic impurities. We report detailed heuristic examination, using model spin-orbit coupled systems, of the emergence of positive AMR (maximum resistivity for magnetization alon…

The chiral anomaly factory: Creating Weyl fermions with a magnetic field

Weyl fermions can be created in materials with both time reversal and inversion symmetry by applying a magnetic field, as evidenced by recent measurements of anomalous negative magnetoresistance. Here, we do a thorough analysis of the Weyl points in these materials: by enforcing crystal symmetries, we classify the location and monopole charges of Weyl points created by fields aligned with high-symmetry axes. The analysis applies generally to materials with band inversion in the $T_d$, $D_{4h}$ and $D_{6h}$ point groups. For the $T_d$ point group, we find that Weyl nodes persist for all directi…

Magnetic anisotropy in strained manganite films and bicrystal junctions

Transport and magnetic properties of LSMO manganite thin films and bicrystal junctions were investigated. Manganite films were epitaxially grown on STO, LAO, NGO and LSAT substrates and their magnetic anisotropy were determined by two techniques of magnetic resonance spectroscopy. Compare with cubic substrates a small (about 0.3 persentage), the anisotropy of the orthorhombic NGO substrate leads to a uniaxial anisotropy of the magnetic properties of the films in the plane of the substrate. Samples with different tilt of crystallographic basal planes of manganite as well as bicrystal junctions …