Effect of partial magnetic order on resistivity and thermopower of Ho(Co1-xAlx)2 alloys

T. Nakama, C. Zukeran, A. Nakamura, A. Teruya, S. Hirakawa, S. Watanabe, Y. Hiranaka, M. Takeda, M. Hedo, K. Yagasaki, Y. Takaesu, K. Uchima, A. T. Burkov

Research output: Contribution to journalArticle

Abstract

The electrical resistivity ρ and the thermopower S of Ho(Co1-xAlx)2 alloys (x = 0 to 0.2) were measured at temperatures from 2 K to 300 K in magnetic fields up to 10 T. While ρ(T) and S(T) of pure HoCo2 reveal abrupt changes at the magnetic ordering temperature T C, indicating a firstorder transition, the temperature variations of both properties across the ordering temperature in Ho(Co1-xAlx)2 alloys clearly show that the type of magnetic transition changes under substitution of Al for Co from first order to second order around x ≈ 0.06. ρ(T) of the Al-substituted samples (x = 0.15 and 0.2) has a very unusual variation at temperatures below TC: in contrast to the expected and usually-observed decrease of ρ(T), the resistivity of Ho(Co1-xAlx)2 alloys (x = 0.15 and 0.2) increases at temperatures below T C. Moreover, the magnetoresistance of these alloys is positive around T C; this is also in a sharp contrast to the usually observed negative magnetoresistance. We show that the anomalous resistivity and magnetoresistance in these alloys are related to the metamagnetic instability of the Co 3d subsystem and to the fluctuating local magnetic susceptibility due to atomic substitution. Due to this fluctuating local magnetic susceptibility, the uniform exchange field of 4f moments induces a non-uniform polarization of the 3d system, with static spatial fluctuations of the local magnetization. This static magnetic disorder gives an additional contribution (ρ m) to the electrical resistance in the alloys at temperatures below T C. The degree of this disorder changes with decreasing temperature, resulting in specific variation of ρ m with temperature.

Original languageEnglish
Pages (from-to)372-376
Number of pages5
JournalJournal of the Korean Physical Society
Volume63
Issue number3
DOIs
Publication statusPublished - 2013 Aug 1
Externally publishedYes

Keywords

  • Electrical resistivity
  • Magnetoresistance
  • Thermopower

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Fingerprint Dive into the research topics of 'Effect of partial magnetic order on resistivity and thermopower of Ho(Co<sub>1-x</sub>Al<sub>x</sub>)<sub>2</sub> alloys'. Together they form a unique fingerprint.

  • Cite this

    Nakama, T., Zukeran, C., Nakamura, A., Teruya, A., Hirakawa, S., Watanabe, S., Hiranaka, Y., Takeda, M., Hedo, M., Yagasaki, K., Takaesu, Y., Uchima, K., & Burkov, A. T. (2013). Effect of partial magnetic order on resistivity and thermopower of Ho(Co1-xAlx)2 alloys. Journal of the Korean Physical Society, 63(3), 372-376. https://doi.org/10.3938/jkps.63.372