Eur. Phys. J. B 45, 237-242 (2005)
https://doi.org/10.1140/epjb/e2005-00181-8

Structural and magnetic properties of ion-beam deposited NiFe/Co-oxide bilayers

Department of Materials Engineering, National Chung Hsing University, Taichung 402, Taiwan, R.O.C.

Corresponding author: ^a kwlin@dragon.nchu.edu.tw

Received: 15 September 2004
Revised: 18 May 2005
Published online: 28 June 2005

Abstract

The structural and magnetic properties of NiFe/Co-oxide bilayers were studied. XRD investigation indicates the NiFe (Permalloy) layers (a= 3.53 Å) grow with a (111) preferred orientation. The Co-oxide layers were fabricated with oxygen content in the deposition assist beam ranging from 8% (rock-salt CoO, a= 4.27 Å) to 34% (spinel Co₃O₄, a= 8.21 Å). Both the coercivity H_c and exchange bias field H_ex closely follow an inverse NiFe thickness relationship. A strong temperature dependence of H_c and H_ex is found in these NiFe/Co-oxide bilayers. At T= 289 K, the NiFe/CoO film exhibits an enhanced H_c relative to pure NiFe/Co or NiFe/Co₃O₄ bilayers, an indication of exchange coupling between the NiFe and CoO phases. At T= 10 K, the NiFe/Co₃O₄ film exhibits an exchange-bias loop shift of  Oe that persists to temperatures greater than 30 K (the Néel temperature of bulk Co₃O₄). The transition temperature of the Co₃O₄ film component has increased above the bulk value via exchange coupling with the permalloy. Results indicate that the exchange coupling interaction between FM and AFM layers are responsible for both enhanced coercivity and cross-tie domains.