Spacer-thickness dependence of interlayer exchange coupling in GaMnAs/InGaAs/GaMnAs trilayers grown on ZnCdSe buffers

Abstract

Interlayer exchange coupling (IEC) between GaMnAs layers in GaMnAs/InGaAs/GaMnAs trilayers was studied by magnetization measurements. Minor hysteresis loops are observed to shift in a direction indicating the presence of ferromagnetic (FM) IEC in the structures. The strength of the FM IEC clearly exhibits an exponential decrease with respect to nonmagnetic InGaAs spacer thickness. The fitting of the spacer thickness dependence of the FM IEC to an exponential decay function provides a decay length of 3.3±0.3 nm, which is relatively large compared to metallic multilayers, indicating a long ranged IEC in systems based on GaMnAs.*

Interlayer exchange coupling in ferromagnetic semiconductor trilayers with out-of-plane magnetic anisotropy

“…In the 20 nm sample, J rapidly decreases with increasing temperature, which is in agreement with the conventional behavior of temperature-dependent IEC observed in earlier studies of GaMnAs-based systems 22 . Intriguingly, the FM IEC of the sample with 10 nm (pink solid circles) displays weak temperature dependence, and shows similar magnitudes of J in the two different temperature regimes.…”

“…7 . The values of J obtained for our samples are somewhat smaller than those obtained from GaMnAs-based trilayer systems, which show J in the range between 0 and 9 μ J/m 2 14 , 22 . The relatively weaker IEC obtained in the GaMnAsP-based systems may be due to the incorporation of P, which lowers the valence band relative to the GaAs spacer, so that the holes mediating the IEC feel a higher energy barrier between the two GaMnAsP layers.…”

“…All data measured at 3 K (see the 1 st row) show that Up-ML shifts to the left and Down-ML shifts to the right, indicating the presence of FM IEC between two GaMnAsP layers in all samples at this low temperature. The separation between the Up-ML and Down-ML in the 20 nm sample quickly drops with increasing temperature and becomes nearly zero near 10 K. Such monotonic temperature dependence of the IEC effect is normally observed in ferromagnetically coupled multilayers 22 . However, the 10- and 7-nm samples show a rather different temperature behavior, as seen in the 2 nd and 3 rd columns of Fig.…”

“…In this context, IEC in multilayers composed of GaMnAs layers with out-of-plane easy axes has important implications for magnetic memory devices. IEC of GaMnAs-based systems with perpendicular magnetic anisotropy has recently been addressed using GaMnAs trilayers grown either on GaInAs or on ZnCdSe buffers 20 – 22 , both of which provide tensile strain in the GaMnAs layers, resulting in out-of-plane magnetic easy axes. These studies revealed the presence of FM IEC between the GaMnAs layers, with an exponential decay of the IEC strength as a function of spacer thickness 22 .…”