Anomalous Hall Effect in the (In,Mn)Sb Dilute Magnetic Semiconductor

Abstract

High magnetic field study of Hall resistivity in the ferromagnetic phase of (In,Mn)Sb allows one to separate its normal and anomalous components. We show that the anomalous Hall term is not proportional to the magnetization, and that it even changes sign as a function of magnetic field. We also show that the application of pressure modifies the scattering process, but does not influence the Hall effect. These observations suggest that the anomalous Hall effect in (In,Mn)Sb is an intrinsic property and support the application of the Berry phase theory for (III,Mn)V semiconductors. We propose a phenomenological description of the anomalous Hall conductivity, based on a fielddependent relative shift of the heavy-and light-hole valence bands and the split-off band.PACS numbers: 75.50. Pp, 75.30.Et, As promising candidates for spintronic applications (III,Mn)V dilute magnetic semiconductors have attracted considerable attention during the past few years [1]. In these alloys the Mn 2+ ions provide localized magnetic moments and valence band holes at the same time. The presence of charge and spin degrees of freedom and the carrier mediated nature of the ferromagnetic coupling open a new way to the electrical control of ferromagnetism [2]. Devices based on magnetic semiconductors represent a novel generation of information technology where MRAM functionalities arise simply from bulk properties [3,4]. Moreover, the magnetic state of diluted magnetic semiconductors (DMSs) can be quickly and conveniently characterized by transport measurements by taking advantage of the unusually large anomalous Hall effect (AHE). While AHE is one of the prominent key properties of ferromagnetic semiconductors, it represents a situation of general interest but little firm knowledge.In general, AHE may arise from scattering processes involving spin-orbit coupling. In the skew scattering and side-jump models [5,6,7] the Fermi-surface properties of the charge carriers are important. We test this possibility experimentally by modifying the scattering process via application of hydrostatic pressure.An alternative class of descriptions relates AHE to the Berry phase acquired while the electrons propagate in spin-orbit coupled Bloch bands. In this picture the AHE arises from near degeneracy points of the bands [6,7,8,9,10,11] where interband processes become relevant. Spin-orbit coupling and the lack of inversion symmetry may result in this type of AHE even for collinear ferromagnets [10]. Our high magnetic field experiments aim to reveal an AHE contribution arising from the relative displacement of the various spin-up and spin-down bands.InSb has the largest spin-orbit coupling among the III-V semiconductors, and becomes a ferromagnetic metal a when few percent of Mn 2+ ions are inserted into the In + sites [12,13,14,15,16]. The band structure is well known [17], including the parameters of the partially filled heavy hole (hh) and light hole (lh) bands. (In,Mn)Sb is an ideal system to study AHE, and our purpose is to distinguish between the poss...

Transport theory for disordered multiple-band systems: Anomalous Hall effect and anisotropic magnetoresistance

“…͑46͔͒. These types of changes of signs have also been observed in experimental systems, e.g., DMS, 52 and of course at that stage scaling is not justified.…”

Anomalous Hall Effect in Field-Effect Structures of (Ga,Mn)As

“…In fact, a negative sign of the R yx has been observed in films of (In,Mn)As [12,13], (In,Mn)Sb [15,16], and (Ga,Mn)Sb [17], where the bulk asymmetry is expected to be much stronger. However, the striking behavior of R yx (T ), including the change of sign revealed here, has not been anticipated theoretically [4,5].…”

Scaling relations between anomalous Hall and longitudinal transport coefficients in metallic (Ga,Mn)As films

“…A similar relation, σ xy ∝ M (1 − αM ), where α is a constant, has been predicted theoretically on the basis of the Berry phase 5 , and confirmed in (In,Mn)Sb by studying the field dependent anomalous Hall effect 40 . Such relationship was explained by assuming that as the field is varied, the relative position of the bands shifts linearly with the absolute value of the magnetization (due to exchange splitting), thus resulting in the anomalous Hall coefficient which will also be linear with M .…”

“…4(b), which clearly shows that the anomalous Hall coefficient χ S is not a constant, but increases rapidly with T at temperatures above T C . A possible explanation for this behavior can be found by introducing the Berry phase 5 , which has been shown to exist in the closely related system (In,Mn)Sb 40 , into the present context. However, this requires further examination.…”