Exchange biasing in ferromagnet/antiferromagnet Fe/KMnF3

A new ferromagnet/antiferromagnet bilayer system, Fe/KMnF3, exhibits intere sting interfacial exchange properties. The bulk antiferromagnet KMnF3 has t hree possible magnetic states: paramagnetic, antiferromagnetic, and weakly ferromagnetic spin-canted. Consequently, the exchange, anisotropy in Fe/KMn F3 is unusual. We examine the exchange bias in Fe/KMnF3 as a function of th e magnetic state. Monocrystalline Fe(0 0 1) and polycrystalline Fe films, 3 nm thick, were grown epitaxially on Ag(0 0 1) templates on GaAs(0 0 1) sub strates. Epitaxial KMnF3 was then grown an both the single-crystal and poly crystal Fe. We measured the low-field, zero-held-cooled and field-cooled ma gnetizations as functions of temperature. The zero-held-cooled single-cryst al Fe magnetization is greatly reduced at liquid-helium temperatures. We se e the influence of the transition from the antiferromagnetic to the spin-ca nted stale on the exchange coupling. The blocking temperature is close to t he Neel temperature (89 K). From the shift in the hysteresis loop, we estim ate the strength of the interfacial exchange coupling to be 4.5 x 10(-5) J/ m(2). (C) 1999 Elsevier Science B.V. All rights reserved.