Harvey A. Alperin

Spin‐Wave Dispersion Relation in Fe‐Ni Alloys

Spin‐wave dispersion in Permalloys of composition Fe0.2Ni0.8 and Fe0.5Ni0.5 was investigated by neutron‐scattering methods. Values of D in the expression for the spin‐wave energy, ħω = Dq2(1−βq2), were found to agree with spin‐wave resonance measurements, but the quartic coefficients β were an order of magnitude smaller.

Magnetic Structure of RbNiF3

Magnetic measurements1 on hexagonal RbNiF3 indicate that this compound exhibits a spontaneous moment of approximately ⅓ the total Ni2+ moment, in contrast to the isomorphous compound CsMnF3, which is antiferromagnetic.2 In this structure (space group C63/mmc) there are two inequivalent cation sites (2a and 4f), and it has been suggested1 that the moment arises from antiparallelism of the cation spins on these two sites. Alternatively, canting of successive antiparallel c planes (such as occur in CsMnF3) toward each other within the plane could account for the observations. Powder and single‐crystal neutron data on RbNiF3 have been obtained which indicate that neither of these two simple models can be correct. A more general model with different canting angles for the 2a and the 4f sublattices, however, is consistent with both neutron and magnetic data.