Suppression of biquadratic coupling at the Cr Néel temperature in Fe/Cr(001) superlattices (invited) (abstract)

We present the effects of antiferromagnetic (AF) order of the Cr spacers in Fe/Cr(001) superlattices on the interlayer coupling of the Fe layers. AF order of the Cr spacers is suppressed for layer thicknesses less than 42 A. For ≳42 A of Cr, the Neel temperature (TN) increases rapidly and asymptotically approaches the bulk value for thick Cr spacers as characterized by a transition‐temperature shift exponent λ=1.4±0.3. Neutron diffraction confirms both the AF order of the Cr layers in superlattices with 62, 100, and 200 A thick Cr layers, and the existence of the incommensurate, transverse spin‐density‐wave magnetic structure whose nesting wave vector is equal to that of bulk Cr. The AF ordering of the Cr results in anomalies in a variety of magnetic properties, including the interlayer coupling, remanent magnetization, coercivity, and magnetoresistance. Most strikingly, the 90° or ‘‘biquadratic’’ coupling of the Fe layers observed for T≳TN is suppressed below TN as confirmed by polarized neutron reflecti...