Competition between ferromagnetism and antiferromagnetism: origin of large magnetoresistance in polycrystalline SrRu1-xMnxO3 (0 le x le 1)

Polycrystalline SrRu1−x MnxO3 (0 x 1) perovskite oxides have been prepared by a conventional solid-state reaction technique. Magnetic and magnetotransport properties are measured using a superconducting quantum interference device (SQUID, Quantum Design MPMS) over a temperature range of 4–300 K. The substitution of Mn ions for Ru drives the system from a ferromagnetic state, SrRuO3, to an antiferromagnetic state, SrMnO3, which is basically similar to observations in single-crystal SrRu1−x MnxO3 (Cao et al 2005 Phys. Rev. B 71 035104). However, the measurement of dc magnetization and ac susceptibility indicates that magnetic phase transition with x is more complicated and pronounced than those in single crystals. The phase transition process as temperature is reduced covers paramagnetism–antiferromagnetism (PM–AFM), paramagnetism–ferromagnetism (PM–FM) and ferromagnetism– cluster glass–spin glass (FM/CG/SG) etc. In particular, we observe a large lowtemperature magnetoresistance (MR) of −41% for the sample x = 0.55, which is the largest MR measured in Mn-doped SrRuO3. The experiment has verified that the large MR stems predominantly from a unique spin glass state in the polycrystalline alloy. These results substantiate that Ru-based oxides doped with 3d/4d transition metals have the potential for use in spintronics devices due to their adjustable phase transition, depending upon the level and nature of 3d/4d ion doping. 4 Author to whom any correspondence should be addressed. 0953-8984/07/266211+15$30.00 © 2007 IOP Publishing Ltd Printed in the UK 1 J. Phys.: Condens. Matter 19 (2007) 266211 X-Y Zhang et al