We studied the interlayer coupling in the quadrilayer consisting of IrMn/CoFe (bottom layer)/NiFeOx/ CoFe (top layer). The in-plane perpendicular interlayer coupling is observed between CoFe layers at room temperature. An anisotropy transition from uniaxial to unidirectional in the perpendicular direction is observed around Tt = 55 K. The nano-oxide layer NiFeOx shows no distinguishable ferromagnetic signal in the high-temperature (uniaxial) phase, while a strong signal appeared in the low-temperature (unidirectional) phase. A possible two-component scenario, that the nano-oxide layer may contain both amorphous short-range antiferromagnetic domains and superparamagneitc clusters, is proposed to explain the phase transition.
@article{arxiv.cond-mat/0607199,
title = {Uniaxial to unidirectional transition of perpendicular interlayer coupling in IrMn/CoFe/NiFeO/CoFe quadrilayers},
author = {Yu-Jen Wang and Chih-Huang Lai and Po-Hsiang Huang and Hsiu-Hau Lin and Chih-Ta Shen and S. Y. Yang and T. S. Chin and Tzay-Ming Hong and H. J. Lin and C. T. Chen},
journal= {arXiv preprint arXiv:cond-mat/0607199},
year = {2009}
}
Comments
final version to appear in Applied Physics Letters