Observation of unusual ferromagnetic cluster glass behavior in CrAlGe

Abstract

We report on an experimental study on the structural and magnetic properties of the intermetallic compound CrAlGe. The material has been investigated in detail by x-ray diffraction, dc magnetization, ac susceptibility, and electrical resistivity measurements. X-ray diffraction and associated Rietveld analysis show that the compound crystallizes in the orthorhombic $\mathrm{TiS}{\mathrm{i}}_{2}\text{\ensuremath{-}}\mathrm{type}$ structure, with lattice parameters $a=4.7531(1)\phantom{\rule{0.16em}{0ex}}\AA{},\phantom{\rule{0.16em}{0ex}}b=8.2182(1)\phantom{\rule{0.16em}{0ex}}\AA{}$, and $c=8.6951(1)\phantom{\rule{0.16em}{0ex}}\AA{}$. The magnetization measurements demonstrate that the alloy is ferromagnetic with a Curie temperature of ${T}_{\mathrm{C}}\ensuremath{\approx}80\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. At 5 K the magnetization saturates at 50 kOe with a saturation moment of ${M}_{\mathrm{S}}=19\phantom{\rule{0.16em}{0ex}}\mathrm{emu}/\mathrm{g}$. Below ${T}_{\mathrm{C}}$, the ac susceptibility data exhibit two distinct frequency dependent peaks, which are also strongly dependent on ac field amplitude and dc magnetic fields. The experimental results strongly suggest the coexistence of ferromagnetic and reentrant spin glass type states in CrAlGe, which is due to the effect of the structural disorder in the $16f$ site (mixed Al/Ge occupation) on the crystallographically ordered $8a$ site of Cr. To our knowledge, CrAlGe is the first example where such unusual magnetic behavior is brought about not by structural disorder on the site occupied by the magnetic atom, but is due to the disorder in the atomic sites of the neighboring atoms.