Spin-gapless semiconducting nature of Co-rich Co1+xFe1xCrGa

Deepika Rani, Enamullah, Lakhan Bainsla, K. G. Suresh, and Aftab Alam
Phys. Rev. B 99, 104429 – Published 25 March 2019

Abstract

Spin gapless semiconductors (SGSs) are an interesting class of materials which bridge the gap between semiconductors and half-metallic ferromagnets. This class of materials shows band gap in one of the spin channels and a zero band gap in the other, and thus promote tunable spin transport. Here, we present structural, electronic, magnetic, and transport properties of Co-rich SGS Co1+xFe1xCrGa using both theoretical and experimental techniques. The key advantage of Co-rich samples Co1+xFe1xCrGa is the high Curie temperature (TC) and magnetization, without compromising the SGS nature (up to x=0.4), and hence our choice. The quaternary Heusler alloys Co1+xFe1xCrGa(x=0.1 to 0.5) are found to crystallize in LiMgPdSn-type structures having space group F4¯3m (number of 216). The measured Curie temperature increases from 690 K (x=0) to 870 K (x=0.5). The obtained TC for x=0.3 (790 K) is found to be the highest among all previously reported SGS materials. Observed magnetization values follow the Slater-Pauling rule. Measured electrical resistivity, in the temperature range of 5–350 K, suggests that the alloys retain the SGS behavior up to x=0.4, beyond which it reflects metallic character. Unlike conventional semiconductors, the conductivity value (σxx) at 300 K lies in the range of 2289 S cm1 to 3294 S cm1, which is close to that of other reported SGS materials. The anomalous Hall effect is comparatively low. The intrinsic contribution to the anomalous Hall conductivity increases with x, which can be correlated with the enhancement in chemical order. The anomalous Hall coefficient is found to increase from 38 S/cm for x=0.1 to 43 S/cm for 0.3. Seebeck coefficients turn out to be vanishingly small below 300 K, another signature for being SGS. All the alloys (for different x) are found to be both chemically and thermally stable. Simulated magnetization agrees fairly with the experiment. As such, Co-rich CoFeCrGa is a promising candidate for room temperature spintronic applications, with enhanced TC, magnetic properties, and SGS nature.

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  • Received 30 November 2018
  • Revised 20 February 2019

DOI:https://doi.org/10.1103/PhysRevB.99.104429

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Deepika Rani1, Enamullah1, Lakhan Bainsla1,2, K. G. Suresh1, and Aftab Alam1,*

  • 1Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India
  • 2WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

  • *aftab@iitb.ac.in

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Issue

Vol. 99, Iss. 10 — 1 March 2019

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