ac Magnetization Transport and Power Absorption in Nonitinerant Spin Chains

We investigate the ac transport of magnetization in nonitinerant quantum systems such as spin chains described by the $XXZ$ Hamiltonian. Using linear response theory, we calculate the ac magnetization current and the power absorption of such magnetic systems. Remarkably, the difference in the exchange interaction of the spin chain itself and the bulk magnets (i.e., the magnetization reservoirs), to which the spin chain is coupled, strongly influences the absorbed power of the system. This feature can be used in future spintronic devices to control power dissipation. Our analysis allows us to make quantitative predictions about the power absorption, and we show that magnetic systems are superior to their electronic counterparts.

Figure 1

Schematic of a quantum spin chain coupled to magnetization reservoirs. The magnetic field bias $\Delta B$ changes periodically in time. In the upper part of the figure, we illustrate that the exchange coupling in the spin chain $J_{\mathrm{sc}}$ (for $|x|<L/2$) can, in general, be different from the exchange coupling in the gray-shaded magnetization reservoirs $J_{\mathrm{res}}$. As suggested in Ref. 6, this setup can be realized by a bulk material with an intrachain exchange much stronger than the interchain exchange, where the material is heated to a temperature $T>T_N$ in the central part and cooled to $T\ll T_N$ in the reservoir parts. ($T_N$ is the 3D Néel ordering temperature.)

Figure 2

The absorbed power is shown in units of $W_0\equiv (g_e{\mu }_B\Delta B{)}^2/2h$ as a function of the ac frequency $\omega$ in units of the ballistic frequency ${\omega }_L=v_w/L$. It is clearly visible that stronger repulsive interactions inside the wire decrease the absorbed power in the system.