Magnetic properties of three-layer superlattices and three-layer systems

Abstract

By employing retarded Green functions, the spin-wave spectrum and the layer-sublattice magnetization in Heisenberg ferrimagnetic three-layer superlattices and three-layer systems are calculated within the framework of the linear spin-wave approximation. The effects of the interlayer exchange constants and the intralayer exchange constants on the magnetic properties of the two systems are compared with those for the corresponding three-sublattice bulk ferrimagnets. It is found that all the differences between the magnetic properties of these systems originate from the differences between the exchange couplings in the three dimensions of the systems. The quantum correlations, such as the competition, cancellation, and transmission of the effects of the exchange couplings, are important for the magnetic properties of the systems. The asymmetry of the systems plays an important role in the zero-point quantum fluctuations and, correspondingly, in the layer-sublattice magnetizations of the layers.

Sublattice Magnetization, Internal Energy, and Specific Heat of Magnetic Three-Layer Superlattices and Two-Dimensional Three-Layer Systems

“…When the S value is small, the quantum effects are obvious, and the zero-point quantum fluctuations reach the maximum at S 1 = S 2 --S 3 . The zero-point quantum fluctuations and the layer-sublattice magnetizations in each layer of both the three-layers and the three-layer superlattices depend sensitively on the competition among the interlayer exchange couplings J 12 , J 23 , and J 13 [23]. It was found in our previous work [23] that the quantum correlations, such as the competition, cancellation, and transmission of the effects of the exchange couplings, are important for the magnetic properties of the systems.…”

“…4a in Ref. [23] for the J 12 dependence of the layer-sublattice magnetization M 20 at zero temperature, which is attributed to the competition among the three interlayer exchange couplings. The solid curve in Fig.…”

“…(Refer to our recent work [19,23] for a detailed description of the procedure.) Applying the spectral theorem, one can obtain the magnetization at zero temperature (T = 0 K) of the three-layer superlattices and the three-layer systems as…”

“…[19] (and the parameters H ij (i, j = 1, 2, 3) are the same as in Ref. [23]). At T = 0 K, the ground state energy per site of the superlattices and the three-layer system is obtained from Eq.…”

“…The spin-wave spectra, the low-temperature magnetization, and the effects of the exchange constants on the magnetization have been investigated in our recent papers [19,23]. In this work, we focus on the effects of the spin values on the magnetization at zero temperature, and also on the effects of the exchange constants, the spin values, and the temperature on the internal energy and the specific heat.…”