Spin Current Generation Controlled by the Néel State in a Compensated Ferrimagnet

Abstract

Compensated ferrimagnets, which break sublattice and time-reversal symmetries in the ground state, exhibit an isotropic ferromagnet-like spin splitting despite a vanishing net magnetization, in contrast to altermagnets with momentum-dependent spin splitting. We investigate how isotropic spin splitting manifests in spin transport by analyzing the spin Seebeck effect and spin pumping in a junction between a compensated ferrimagnet and a normal metal. We show that compensated ferrimagnets generate a sizable spin Seebeck signal, with a sign that can be reversed by switching between the two Néel states. Furthermore, we demonstrate that spin pumping exhibits a Néel-state-dependent resonance splitting, which is absent in conventional antiferromagnets. These results identify spin pumping as a natural readout mechanism for compensated ferrimagnets and establish them as promising magnetization-free building blocks for spintronic memory devices.

Figures (4)

• Figure 1: Schematic illustration of a compensated-ferrimagnet--normal-metal (CF--NM) junction. (a) Spin Seebeck effect. (b) Spin pumping.
• Figure 2: (a) Magnon dispersion of a compensated ferrimagnet for $K_{\rm A} = 0.1J$ and $K_{\rm B} = 0.04J$, exhibiting uniform isotropic spin splitting along the momentum paths shown in the inset.
• Figure 3: Temperature dependence of the spin current in the CF--NM junction normalized by $P=4S_0 Ak_{\rm B}\Delta T$. The parameters are chosen as $K_{\rm A}=\bar{K}+\Delta K/2$ and $K_{\rm B}=\bar{K}-\Delta K/2$, and the solid lines correspond to $\Delta K/\bar{K} = 0, 0.08, 0.16, 0.24$, and 0.32 for $\bar{K} = 0.005J$. The dashed lines correspond to the case where the magnetizations on the A and B sublattices are flipped for finite $\Delta K$. These curves are obtained by exchanging the anisotropy parameters between sublattices A and B. The dotted line shows the result for the FI--NM junction.
• Figure 4: Normalized spin current generated by spin pumping as a function of frequency $\Omega$ for $K_{\rm A}=0.006J$, $K_{\rm B}=0.004J$, and $\alpha_{\rm G}=10^{-3}$, where $\alpha_{\rm G}$ denotes the Gilbert damping constant. (a) Spin current for a circularly polarized microwave field, $I_{\rm SP}(\Omega)/I_0$. (b) Spin current for a linearly polarized microwave field, $(I_{\rm SP}(\Omega) + I_{\rm SP}(-\Omega))/2I_0$. $I_0$ is the maximum value of the peak of Eq .\ref{['eq:spinpumpingspincurrent']}