Experimental identification of domain-wall-center and domain-wall-edge NMR resonances in magnetically ordered materials

Abstract

The effect of an external magnetic field, applied perpendicular to the $c$ axis, on the $^{59}\mathrm{Co}$ spinecho intensity has been measured for hcp Co and Y${\mathrm{Co}}_{5}$. The resulting reduction in the echo intensity for hcp Co is largest in that portion of the spectrum associated with the domain-wall center and monotonically approaches zero at the lower edge of the spectrum which is associated with the domain-wall edge. A technique is presented which allows one to make a direct experimental determination of whether a NMR resona\ifmmode \dot{}\else \.{}\fi{}nce peak observed in a magnetically ordered material is of the domain-wall-center or domain-wall-edge type. Such an identification will be necessary for a microscopic analysis of the Co sublattice contribution to the magnetocrystalline anisotropy in the $R{\mathrm{Co}}_{5}$ compounds. The two observed peaks in the $^{59}\mathrm{Co}$ NMR spectrum of Y${\mathrm{Co}}_{5}$ are both domain-wall-center resonances and arise from the two inequivalent Co sites.