Influence of complex disorder on skew-scattering Hall effects inL10-ordered FePt alloy

Abstract

We show by first-principles calculations that the skew-scattering anomalous Hall and spin-Hall angles of L10-ordered FePt drastically depend on different types of disorder. A different sign of the AHE is obtained when slightly deviating from the stoichiometric ratio towards the Fe-rich side as compared to the Pt-rich side. For stoichiometric samples, short-range ordering of defects has a profound effect on the Hall angles and can change them by a factor of 2 as compared to the case of uncorrelated disorder. This might explain the vast range of anomalous Hall angles measured in experiments, which undergo different preparation procedures and thus might differ in their crystallographic quality.Future information technology will heavily rely on spin-orbit effects, which enable the all-electric control of magnetization and spin-degrees of freedom. Spin currents already play a vital role in state-of-the-art technology, for example in spin-transfer torque magnetic access memories (STT-MRAM), and will become ever more important in emergent magnetic technologies. Bright prospects of relativistic spin currents are associated in particular with their key importance for the phenomena of spin-orbit torque [1], current-induced domain wall [2] and skyrmion motion [3], and ultrafast magnetic applications [4].At the heart of spin-orbit transport effects lie the anomalous and spin Hall effects (AHE and SHE) [5], because they allow for an efficient conversion from a longitudinal charge current (that is, aligned parallel to an applied electric field) into a transverse charge and spin current, respectively. For these microscopically spinorbit coupling (SOC) originated phenomena there is already a relatively established knowledge of their underlying mechanisms, which partly root in topological properties, thus fundamentally relating the AHE and SHE to the physics of e.g. skyrmions [6], orbital magnetism [7] and topological metals [8]. Conventionally, three relatively distinct contributions to the AHE and SHE are discussed: the so-called intrinsic Berry phase contribution stemming from the electronic structure of a pristine crystal, and two contributions which arise due to disorder, namely, the side-jump and skew-scattering [9]. Among the three, it is the skew scattering which dominates the Hall effects in the limit of small disorder. The reason is the linear scaling of the skew-scattering driven transverse conductivity σ xy with the diagonal conductivity σ xx for vanishing scattering. The corresponding scaling constants, the so-called anomalous or spin Hall angles, AHA or SHA, are respectively defined as α AHE = σ From a materials perspective, while elemental ferromagnets Fe, Co and Ni give rise to relatively large AHE, they have the disadvantage of weak SOC with corresponding small values of magnetic anisotropy energy [10,11]. Heavy transition-metals with strong SOC can be successfully doped with magnetic impurities and give rise to large AHE, however, such systems suffer from low Curie temperatures [12]. The L1 0 -ordered FePt allo...

Bulk Spin Torque‐Driven Perpendicular Magnetization Switching in L10 FePt Single Layer

“…[5][6][7] The former, i.e., spin-orbit coupling (SOC), is also the premise of recently discovered spin-orbit torque (SOT) effect, [8][9][10] which opens new avenues for the possible electrical manipulation of magnetization for L1 0 FePt. [11][12][13] However, the emergence of SOT has hitherto been associated with the inversion symmetry breaking that happens either at the normal metal/ferromagnet interface or inside bulk ferromagnets with non-centrosymmetric structures. [9,10,14,15] L1 0 FePt is a centrosymmetric alloy that does not exhibit symmetry breaking for either the global crystal or for specific atomic sites; therefore, the electric current-induced spin polarization tends to vanish in L1 0 FePt from the perspective of crystalline symmetry.…”

Intricate features of electron and hole skew scattering in semiconductors

“…The physical picture of the skew scattering and AHE becomes more complicated when both an impurity has a complex inner structure and the electronic band structure is modified by SOC. To date this situation has been mostly considered for metallic systems via first-principles calculations [19][20][21][22]. A particularly interesting situation occurs when the impurity has an inner magnetic moment.…”

Defect-implantation for the all-electrical detection of non-collinear spin-textures

“…In the context of spintronics 1 exploiting the spin rather than the charge to carry information, defects can reduce the efficiency of magnetoresistance effects 2,3 in current perpendicular-to-plane geometries such as the giant magnetoresistance (GMR) 4,5 or tunneling magnetoresistance (TMR) 6,7 . Impurities intrinsically can alter the conductance by increasing it or reducing it, as shown for various constrictions [8][9][10][11] , giving rise to inelastic transport channels allowing the exploration of electron-bosons interactions [12][13][14] while generating extrinsic contributions to Hall effects [15][16][17][18][19][20] in current-in-plane geometries. All of this is not surprising since the very fundamental Kondo effect 21 results from diluted magnetic impurities leading to an anomalous behavior of the resistance at low temperature 22 .…”