Sign reversal and manipulation of anomalous Hall resistivity in facing-target sputtered Pt/Mn_(4)N bilayers

The magnetic and electronic transport properties manipulated by spin-orbit torque have been devoted much attention as they show a great promise for future spintronic devices.Here,the spin dependent transport properties of the facing-target sputtered Pt/Mn_(4)N bilayers on MgO(001)substrates have been investigated systematically.The Hall resistivity of Pt/Mn_(4)N bilayers is strongly dependent on temperature,applied current intensity,Mn_(4)N and Pt layer thicknesses.The temperature-dependent sign reversal of anomalous Hall resistivity appears in Pt/Mn_(4)N bilayers,which is dominated by the competition between the magnetic proximity and spin Hall effects.Besides,the magnitude of anomalous Hall resistivity can be manipulated by applied current density.The critical and saturation currents are related to Mn_(4)N and Pt layer thicknesses.Furthermore,a Dzyaloshinskii-Moriya interaction coefficient(D)of 5.63 mJ·m^(-2)is calculated in Pt/Mn_(4)N/MgO systems.The details of the anomalous Hall effects in Pt/Mn_(4)N bilayers are helpful to understand the interfacial effects between heavy metals and ferrimagnets.

Generation and manipulation of skyrmions and other topological spin structures with rare metals

Skyrmions are nano-scale quasi-particles with topological protection,which have potential applications in next-generation spintronics-based information storage.Numerous papers have been published to review various aspects of skyrmions,including physics,materials and applications.However,no review paper has focused on rare metals which play important roles in nucleating and manipulating skyrmions and other topological states.In this paper,various roles of rare metals have been classified and summarized,which can tune Curie temperature(TC),Dzyaloshinskii-Moriya interaction(DMI),magnetocrystalline anisotropy,Ruderman-Kittel-Kasuya-Yosida(RKKY)interaction and four-spin interaction so as to trigger the generation of skyrmions and other topological spin structures.The materials covered include typical B20 crystals,various layered systems with interfacial DMI,frustrated materials,antiferromagnets,ferrimagnets,twodimensional(2D)materials,etc.In addition,the rare-earth(RE)permanent magnets can provide an energy barrier and enrich the dynamic behaviors of skyrmions,which has also been reviewed.

Abnormal low-field M-type magnetoresistance in hexagonal noncollinear ferromagnetic MnFeGe alloy

The new magnetic degree of freedom provided by the noncollinear structure plays an important role in the development of spintronic devices.In this work,we conducted a systematic study on the magnetic and electrical transport properties of the hexagonal noncollinear ferromagnetic MnFeGe alloy.Abnormal Hall effect and moderate magnetoresistance(MR)were observed below the Curie temperature(~200 K)of MnFeGe,in both bulk and thin-film forms.Notably,the perpendicular MR in all samples firstly grows,then quasi-linearly descends with magnetic field increasing,making an irregular M-type MR in the low-field region.It is speculated that the abnormal MR is related to the magnetic domain change,and combined with micromagnetic simulations,the labyrinth domain and sparse bubble formation are verified to exist in MnFeGe.Our work offers an understanding of the lowfield-positive MR in a ferromagnet,as well as raises the possibility of magnetic bubble formation in this noncollinear system.

Electric field manipulation of magnetic skyrmions

Magnetic skyrmions are vortex-like swirling spin textures that are promising candidates for carrying information bits in future magnetic memories or logic circuits.To build skyrmionic devices,researchers must electrically manipulate magnetic skyrmions to enable easy integration into modern semiconductor technology.This operation generally uses a spin-polarized current,which unavoidably causes high energy dissipation and Joule heating.Thus,the electric-field strategy is a hopeful alternative for electrically manipulating the skyrmions due to the strategy’s negligible Joule heating and low energy cost.In this review,we systematically summarize the theoretical and experimental development of the electricalfield manipulation of magnetic skyrmions over the past decade.We review the following magnetic systems and physical mechanisms:(ⅰ)ultra-thin multilayer films with accumulation and release of interfacial charge,(ⅱ)singlephase multiferroic material with magneto-electric coupling,(ⅲ)ferromagnetic/ferroelectric(FM/FE)multiferroic heterostructure with magneto-elastic coupling.Finally,we consider future developmental trends in the electric-field manipulation of magnetic skyrmions and other topological magnetic domain structures.