Resonant Hall effect under generation of a self-sustaining mode of spin current in nonmagnetic bipolar conductors with identical characters between holes and electrons

Abstract

We have proposed an enhancement mechanism of the Hall effect, the signal of which is amplified due to the generation of a sustaining mode of spin current. Our analytic derivations of the Hall resistivity revealed the conditions indispensable for the observation of the effect: (i) the presence of the transverse component of an effective electric field due to spin splitting in chemical potential in addition to the longitudinal component; (ii) the simultaneous presence of holes and electrons each having approximately the same characteristics; (iii) spin-polarized current injection from magnetized electrodes; (iv) the boundary condition for the transverse current (J c,y = 0). The model proposed in this study was experimentally verified by using van der Pauw-type Hall devices consisting of the nonmagnetic bipolar conductor YH x (x ' 2) and TbFeCo electrodes. Replacing Au electrodes with TbFeCo electrodes alters the Hall resistivity from the ordinary Hall effect to the anomalous Hall-like effect with an enhancement factor of approximately 50 at 4 T. We interpreted the enhancement phenomenon in terms of the present model.

Spatiotemporal characteristics of spin transport in compensated metals with electron–hole exchange interaction

“…where j (K) ↑ is the current due to spin-up carriers in the valley K [46]. This may explain the anomalous Hall effect like signal from an approximately 10 μm-long YH 2 channel under spin-polarized current injection [47].…”

Entropy production by thermodynamic currents in ambipolar conductors with identical spin dynamics characteristics between holes and electrons

“…( 26) and ( 27) that ℓ AP in an ambipolar metal has a value larger than the spin diffusion lengths in conventional paramagnetic metals by a factor of 1 F if the spin relaxation time s t and the spin diffusion coefficient of the ambipolar metal are approximately the same as those of single-carrier-type paramagnetic metals. When using the spin diffusion length (∼162 nm) of Ag, 22) and Φ value of ∼0.15% of YH 2 , 21) ℓ AP of YH 2 is determined to be approximately 4 μm, which probably explains the observation of the anomalous Hall effect in YH 2 with approximately 10 μm channel length because the spin-polarized hole and electron currents are injected from the source and drain magnetic electrodes, respectively, so that an antiparallel flow configuration is achieved. 21) On the other hand, the holes and electrons in Bi 0.95 Pb 0.05 have the approximately same density of 3 × 10 23 m −3 , 23) yielding Φ ∼ 0.…”

“…When using the spin diffusion length (∼162 nm) of Ag, 22) and Φ value of ∼0.15% of YH 2 , 21) ℓ AP of YH 2 is determined to be approximately 4 μm, which probably explains the observation of the anomalous Hall effect in YH 2 with approximately 10 μm channel length because the spin-polarized hole and electron currents are injected from the source and drain magnetic electrodes, respectively, so that an antiparallel flow configuration is achieved. 21) On the other hand, the holes and electrons in Bi 0.95 Pb 0.05 have the approximately same density of 3 × 10 23 m −3 , 23) yielding Φ ∼ 0. Substitution of Φ ∼ 0 into Eq.…”

“…Since we consider semimetals and compensated metals as ambipolar conductors, degenerate holes and electrons occupy different wave number regions so that they independently contribute to electronic conduction. The reason why we employ ambipolar conductors is that the present study is stimulated by the experimental results on the Hall effect of the paramagnetic ambipolar conductor YH 2 under spin injection, 21) which shows an anomalous Hall effect-like feature at room temperature despite a relatively long channel length (∼10 μm), much larger than the typical spin diffusion length in paramagnetic metals such as Cu. 22) In another report on spin-coherent length in an ambipolar conductor, Lee extended the spin injection technique to semimetal Bi 0.95 Pb 0.05 to report a spin diffusion length of approximately 230 μm at 2 K. 23) These extraordinary characteristics motivate us to investigate the reason behind the ambipolar conductor having an extraordinarily large spin coherent length.…”

Spin-charge-coupled transverse resistance in an ambipolar conductor YH2-based Hall-bar structure with perpendicularly magnetized current-injection electrodes

“…The room-temperature Hall effect of the electron-hole compensated metal, YH 2 , with a channel length of approximately 10 μm was measured using various types of electrodes, including magnetic and nonmagnetic metals. The metal exhibited a hysteresis-loop feature in the Hall voltage when a perpendicularly magnetized Tb 0.26 Fe 0.66 Co 0.08 electrode was utilized as both the current injection and voltage detection electrodes [26]. To investigate the large spin-diffusion length in Bi 1−x Pb x and YH 2 , a thermodynamic model considering the Gibbs-Duhem relation and a microscopic model based on the Baber collision with spin-flipping have been proposed [27,28], although direct experimental verification has not been conducted.…”