Magnetoresistance Generated by Combination of Spin–Orbit Interaction and Applied Magnetic Field in Bipolar Conductors

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

Sakuraba

et al. 2014

Self Cite

Metallic dihydride GdH 2 is known to have an antiferromagnetic phase below 20 K, whereas YH 2 is compensated paramagnetic metal in which not only carrier density but also mobility are the same between electron and hole. Since both GdH 2 and YH 2 have CaF 2 type structure, it is possible to fabricate a single phase of Gd x Y 1-x H 2 with arbitral Gd content (x). The present study is aiming at assessment of carrier effective mass of Gd x Y 1-x H 2 as a function of x. For this purpose, we have carried out (i) the optical reflectivity measurement at photon energy region including the plasma frequency and (ii) calculation of the conduction band density of states, from which carrier density can be estimated. It follows from (i) and (ii) that the reduced mass associated with the electron mass and the hole mass is estimated as a function of x, indicating the maximum value of approximately 6.3 (±0.23) m 0 at x≒0.39. Also another interpretation in terms of the carrier density and mass difference between electrons and holes will be discussed.

Section: Procedures Of Experiments and Analysissupporting

confidence: 79%

Optical Assessment of Carrier Effective Mass in Gd_xY₁₋_xH₂(0 ≦x≦ 1)

Haruyama

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

Sakuraba

et al. 2014

Self Cite

“…When employing the AHE model, we have to consider the carriers of the Gd x Y 1-x H 2 to be spin-polarized, because the unbalance in carrier density between up and down spin states is indispensable to the generation of AHE, the mechanism of which is the left-right asymmetric scattering due to spin-orbit interactions (SOI) [9]. In particular, the positive TMR suggests the Gd x Y 1-x H 2 to be a BCC, because the TMR and HR with carrier spin-polarization are approximately formulated as a function of magnetic field (B) under the two-current model as [3] (2) 3where we assume i) the electron and hole spin is mutually parallel such that the total spin polarization is given as P(=P e +P h ), ii) the carrier density and mobility (μ) are the same between electrons and holes as observed in YH 2 , and iii) the SOI parameter S is substantially larger than B. In addition to the third terms in eq.…”

Section: Discussionmentioning

confidence: 99%

“…In YH 2 , the level of spin polarization due to the Pauli paramagnetism is estimated to be approximately 3% at 5 T from its observed susceptibility (χ Pauli ) [3]. To enhance χ Pauli but remaining the QZHC unchanged, we have fabricated dihydride compounds of Gd-Y alloy [4], because YH 2 and GdH 2 show approximately the same characteristics in terms of crystal structure [5] and electronic structure [6,7] except the presence of 4f electrons in GdH 2 .…”

Section: Introductionmentioning

confidence: 99%

Hall Effect and Magnetoresistance in Gd_xY₁₋_xH₂(x\( \fallingdotseq \) 0.4)

Sakuraba

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

Arai

et al. 2014

Self Cite

We are aiming at the construction of the bipolar conducting system, the holes and electrons of which are spin-polarized such that the spin current is generated through either the ordinary or anomalous Hall effects. Taking advantage of the quasi-zero Hall coefficient characteristic (QZHC) of YH 2 in which electrons and holes have approximately the same carrier density and mobility, Gd was incorporated to form a magnetic QZHC system Gd x Y 1-x H 2 (x=0.39). The zero field specific resistivity (ρ 0), Hall resistivity (HR), and transverse magnetoresistivity (TMR) in Gd x Y 1-x H 2 (x=0.39) were measured as a function of temperature ranging from 4 to 400 K. Huge signals were observed in both HR and TMR around 210 K, well synchronized with the abrupt change observed in ρ 0. Two type of interpretation, i.e., the ordinary Hall and anomalous Hall effect models are given to discuss the feasibility of each mechanism based on our experimental results.

“…The electrical conductivities of spin-up (α) and spin-down ( β) holes=electrons can be derived from the Drude model under the simultaneous presence of B and SOI, the strength of which is expressed by the effective magnetic field S h=e . 20,21) Their formulae are given by…”

Section: Spin and Charge Currents In Bipolar Conductorsmentioning

confidence: 99%

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

Takao

Matsunaga

et al. 2018

Jpn. J. Appl. Phys.

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.