Quantum Spin Effect and Short-Range Order above the Curie Temperature

Abstract

Using quantum Heisenberg model calculations with Green's function technique generalized for arbitrary spins, we found that for a system of small spins the quantum spin effects significantly contribute to the magnetic short-range order and strongly affect physical properties of magnets. The spin dynamics investigation confirms that these quantum spin effects favor the persistence of propagating spin-wave excitations above the Curie temperature. Our investigation suggests a reconsideration of prevailing point of view on finite temperature magnetism to include quantum effects and the magnetic short-range order.