[13p-PA1-1~33] 10 スピントロニクス・マグネティクス（ポスター）

▲ [13p-PA1-23] Positive exchange bias and vertical shift of magnetization curve in Cr₂O₃/Co exchange coupling system

〇Tomohiro Nozaki¹, Satya Prakash Pati¹, Yohei Shiokawa¹, Muftah K O Al-Mahdawi¹, Masashi Sahashi¹ (1.Tohoku Univ.)

キーワード：exchange bias,Cr2O3

Magnetoelectric material Cr₂O₃ has received much attentions as a promising candidate for voltage-controlled spin devices. It is also interesting as a exchange coupling system with unique properties. Before we observed positive-exchange bias (H_ex) phenomena for Cr₂O₃/Pt/Co system. [1] When the cooling filed H_fc during field cool process is sufficient large, spin of Co was pinned against the cooling field direction, i.e. positive-H_ex was obtained, while when H_fc is small, normal negative H_ex is obtained. Negative coupling between ferromagnet and antiferromagnet surface spin and existence of surface magnetization of antiferromagnet were said to be the requirements to observe positive-H_ex. In the previous report, larger H_fc is required to observe positive-H_ex for larger H_ex sample. For example, H_fc ~ 20kOe (3kOe) was required to observe positive-H_ex for samples with H_ex ~ 1000Oe (400Oe). In this study we observed positive-H_ex for sample with very large H_ex (~ 4000Oe) and the H_fc required for positive H_ex was as small as 5kOe. In addition, vertical shift of magnetization curve also observed for this sample. We will discuss the possible reason.
[1] T. Nozaki et al., Appl. Phys. Lett., 105 (2014) 212406.