Experimental evidence of noncollinear magnetism in gadolinium tetraboride

Abstract

Recently, the collinear or noncollinear character of the magnetic structure of gadolinium tetraboride $({\mathrm{GdB}}_{4})$, laying the magnetic moments in the $ab$ plane, becomes a matter of controversy. In the present study, the observations obtained from resistivity, specific heat, and magnetic susceptibility measurements on a single crystal sample contain no evidence for a structural phase transition in this material above or below the N\'eel temperature ${T}_{N}$. In addition to these measurements, the resonant x-ray Bragg diffraction structure factors derived from all the possible arrangements for Gd magnetic moments compatible with the room temperature tetragonal $P4∕mbm$ space group are calculated. The intensity derived with Shubnikov magnetic $P4∕{m}^{\ensuremath{'}}{b}^{\ensuremath{'}}{m}^{\ensuremath{'}}$ and $P{4}^{\ensuremath{'}}∕{m}^{\ensuremath{'}}{b}^{\ensuremath{'}}m$ space groups are found to account for the previously published resonant x-ray diffraction data on ${\mathrm{GdB}}_{4}$. (Both Shubnikov groups have magnetoelectric symmetry.)