Unexpected versatile electrical transport behaviors of ferromagnetic nickel films

Kai-Xuan Zhang; Hanshu Xu; Jihoon Keum; Xiangqi Wang; Meizhuang Liu; Zuxin Chen

doi:10.1088/1361-648X/ad2e25

Unexpected versatile electrical transport behaviors of ferromagnetic nickel films

J Phys Condens Matter. 2024 Mar 13;36(23). doi: 10.1088/1361-648X/ad2e25.

Authors

Kai-Xuan Zhang¹, Hanshu Xu², Jihoon Keum¹, Xiangqi Wang³, Meizhuang Liu⁴, Zuxin Chen^{4

5}

Affiliations

¹ Center for Quantum Materials, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea.
² Department of Applied Physics, School of Biomedical Engineering, Anhui Medical University, Hefei 230032, People's Republic of China.
³ Jihua Laboratory Testing Center, Jihua Laboratory, Foshan 528000, People's Republic of China.
⁴ School of Semiconductor Science and Technology, South China Normal University, Foshan 528225, People's Republic of China.
⁵ Guangdong Provincial Key Laboratory of Chip and Integration Technology, Guangzhou 510631, People's Republic of China.

PMID: 38417165
DOI: 10.1088/1361-648X/ad2e25

Abstract

Perpendicular magnetic anisotropy (PMA) of magnets is paramount for electrically controlled spintronics due to their intrinsic potentials for higher memory density, scalability, thermal stability and endurance, surpassing an in-plane magnetic anisotropy (IMA). Nickel film is a long-lived fundamental element ferromagnet, yet its electrical transport behavior associated with magnetism has not been comprehensively studied, hindering corresponding spintronic applications exploiting nickel-based compounds. Here, we systematically investigate the highly versatile magnetism and corresponding transport behavior of nickel films. As the thickness reduces within the general thickness regime of a magnet layer for a memory device, the hardness of nickel films' ferromagnetic loop of anomalous Hall effect increases and then decreases, reflecting the magnetic transitions from IMA to PMA and back to IMA. Additionally, the square ferromagnetic loop changes from a hard to a soft one at rising temperatures, indicating a shift from PMA to IMA. Furthermore, we observe a butterfly magnetoresistance resulting from the anisotropic magnetoresistance effect, which evolves in conjunction with the thickness and temperature-dependent magnetic transformations as a complementary support. Our findings unveil the rich magnetic dynamics and most importantly settle down the most useful guiding information for current-driven spintronic applications based on nickel film: The hysteresis loop is squarest for the ∼8 nm-thick nickel film, of highest hardness withR_xy^r/R_xy^s∼ 1 and minimumH_s-H_c, up to 125 K; otherwise, extra care should be taken for a different thickness or at a higher temperature.

Keywords: butterfly magnetoresistance; ferromagnetic nickel thin film; magnetic transition; perpendicular magnetic anisotropy (PMA); transport and spintronics.