Magnetic properties of transition metal substituted La 0.85Ag 0.15Mn 1−yM yO 3 compounds (M=Co, Cr and Al)

Abstract

In this paper we report a systematic study of Mn-site substitution by M=Co, Cr and Al in La 0.85Ag 0.15MnO 3 series to understand the magnetic interactions between Mn and other transition metals. The long-range ferromagnetic (FM) ordering of the parent compound was significantly affected by Mn-site substitution. The measured magnetic properties of Co-doped samples have been explained on the basis of FM interactions in Mn 3+–O–Mn 4+, Co 2+–O–Mn 4+, Co 3+–O–Mn 4+ networks and simultaneous antiferromagnetic (AFM) interactions in Mn 4+–O–Mn 4+, Co 2+–O–Mn 3+ networks. The magnetic properties of Cr-doped compounds could be understood on the basis of double exchange FM interactions in Mn 3+–O 2−–Mn 4+ networks and competing AFM in Cr 3+–O–Mn 4+, Mn 4+–O–Mn 4+, Cr 3+–O–Mn 3+ networks. However, it is found that the doping of Al ions play a role of magnetic dilution, without contributing any other competing magnetic interaction. The field variations of magnetization of all the above three series could be analysed by fitting to Brillouin function model and the effective spin contribution for FM has been determined. The measured saturation magnetization has been explained quantitatively.