Spin-glass magnetic ordering in CoMgGaO₂BO₃ ludwigite

Abstract

The single crystal needle shape samples of diamagnetically diluted cobalt ludwigite CoMgGaO₂BO₃ have been grown by the flux method. The results of x-ray diffraction and both dc and ac magnetic measurements are presented. The unit cell volume undergoes a noticable growth under dilution from 328.31 Å3 for the parent compound Co₃O₂BO₃ to 345.46 ų for CoMgGaO₂BO₃. The temperature of magnetic transition is considerably lower for the latter compound (25 K against 43 K for Co₃O₂BO₃). The dc magnetization temperature dependencies undergo the splitting of field cooled and zero-field cooled regimes and the ac magnetic susceptibility temperature dependencies are frequency dependent pointing out a possible spin-glass freezing in the magnetic system.