Exchange interactions between Cr3+ions in magnesium oxide. II. Electron spin resonance spectra

Abstract

For pt.I see ibid., vol.18, p.6397 (1985). Cr3+ions in MgO may cluster in pairs with cation vacancies to form C.MgV"MgCr.Mgneutral dimers, which behave magnetically as exchange-coupled pairs. The authors have identified two different neutral Cr3+dimers in MgO using electron spin resonance (ESR). One is a linear aggregate parallel to (100) directions; the other has a right-angled configuration centred on the vacancy, with each of the impurity-vacancy interactions being in (100) directions. The ESR spectra have been interpreted using exact solutions of the spin Hamiltonian in which the magnetic ions are coupled by two linear terms Js1.s2+De(3(s1.n)(s2.n)-s1Os2). The exchange interactions are both antiferromagnetic with J-values of 0.004+or-0.001 cm-1and 1.5+or-0.05 cm-1for the linear and bent dimers respectively. These values reflect the variation of J with magnetic ion separation in the dimer.