Magnetic phase transition and continuous spin switching in a high-entropy orthoferrite single crystal

Abstract

Rare-earth orthoferrite REFeO₃ (where RE is a rare-earth ion) is gaining interest. We created a high-entropy orthoferrite (Tm_0.2Nd_0.2Dy_0.2Y_0.2Yb_0.2) FeO₃ (HEOR) by doping five RE ions in equimolar ratios and grew the single crystal by optical floating zone method. It strongly tends to form a single-phase structure stabilized by high configurational entropy. In the low-temperature region (11.6–14.4 K), the spin reorientation transition (SRT) of Γ₂ (F_x, C_y, G_z)–Γ₂₄–Γ₄ (G_x, A_y, F_z) occurs. The weak ferromagnetic (FM) moment, which comes from the Fe sublattices distortion, rotates from the a- to c-axis. The two-step dynamic processes (Γ₂–Γ₂₄–r₄) are identified by AC susceptibility measurements. SRT in HEOR can be tuned in the range of 50–60000 Oe, which is an order of magnitude larger than that of orthoferrites in the peer system, making it a candidate for high-field spin sensing. Typical spin-switching (SSW) and continuous spin-switching (CSSW) effects occur under low magnetic fields due to the strong interactions between RE–Fe sublattices. The CSSW effect is tunable between 20–50 Oe, and hence, HEOR potentially can be applied to spin modulation devices. Furthermore, because of the strong anisotropy of magnetic entropy change (−ΔS_m) and refrigeration capacity (RC) based on its high configurational entropy, HEOR is expected to provide a novel approach for refrigeration by altering the orientations of the crystallographic axes (anisotropic configurational entropy).