NEUTRON-DIFFRACTION AND REFLECTIVITY STUDIES OF THE CR NEEL TRANSITION IN FE CR(001) SUPERLATTICES/

The effects on the interlayer coupling of the Cr Nel transition is stu died in Fe/Cr(001) superlattices. The Neel transition is suppressed fo r Cr layer thickness < 42 Angstrom. For > 42 Angstrom of Cr, the Neel temperature T-N initially increases rapidly and then asymptotically ap proaches its bulk value with a three-dimensional transition-temperatur e shirt exponent value of lambda = 1.4 +/- 0.3. Neutron diffraction co nfirms both the Cr antiferromagnetic order and the existence of the in commensurate, transverse spin density wave whose nesting wave vector i s the same as that of bulk Cr. The ordering of the Cr dramatically alt ers the coupling of the Fe layers. The biquadratic Fe interlayer coupl ing observed for T > T-N vanishes below T-N as confirmed by polarized neutron reflectivity. The behavior can be understood in terms of finit e-size and spin frustration effects at rough Fe-er interfaces.