Interlayer exchange coupling between next nearest neighbor layers

Abstract

Interlayer exchange coupling (IEC) between next nearest neighbor magnetic layers is investigated. For a multilayer system that contains threemagnetic layers (with magnetization directionsm (m)over-cap(1), (m)(m)over-cap(2), and (m)(m)over-cap(3), respectively) separated by two nonmagnetic layers, the angle dependence of the coupling energy and the thickness dependence of coupling constants were obtained. In addition to the well known nearest neighbor IEC of the form -(J)over-tilde(12)(m)over-cap(1) center dot (m)over-cap(2) and -(J)over-tilde(23)(m)over-cap(2) center dot (m)over-cap(3), we find the next nearest neighbor IEC of the form -(J) over-tilde(123)((m)over-cap(1) center dot (m)over-cap(2))((m)over-cap(2) center dot (m)over-cap(3)), which is different from the Heisenberg type next nearest neighbor coupling -J(13)(m)over-cap(1) center dot (m)over-cap(3). The strength of the next nearest neighbor IEC oscillates with respect to the thickness of both magnetic and nonmagnetic layers. The strength of the next nearest neighbor IEC is generally smaller than the conventional nearest neighbor IEC, but is large enough to allow for experimental detection.