Reentrant superspin glass state and magnetization steps in the oxyborate Co2AlBO5

Abstract

An oxyborate Co2AlBO5 belonging to the ludwigite family is investigated using structural, thermodynamic, dielectric, and magnetic measurements. Magnetic measurements indicate that this system is seen to exhibit long-range magnetic ordering at TN=42K, signatures of which are also seen in the specific heat, dielectric susceptibility, and lattice parameters. The absence of a structural phase transition down to the lowest measured temperatures distinguishes it from the more extensively investigated Fe-based ludwigites. At low temperatures, the system is seen to stabilize in a reentrant superspin glass phase at TG=10.6K from within the magnetically ordered state. This ground state is also characterized by magnetic-field-induced metamagnetic transitions, which at the lowest measured temperatures exhibit a number of sharp magnetization steps, reminiscent of that observed in the mixed valent manganites.