Title: Probing the spin-glass and magnetoresistance in FeSr₂Y_1.7Ce_0.3Cu₂O_10-δ

Authors: S. Sambale; G.V.M. Williams; S.V. Chong

Addresses: School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand; Robinson Research Institute, Victoria University of Wellington, P.O. Box 33436, Lower Hutt, New Zealand ' School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand ' The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand; Robinson Research Institute, Victoria University of Wellington, P.O. Box 33436, Lower Hutt, New Zealand

Abstract: We have measured the electronic transport and magnetic properties of the rare-earth doped iron-cuprate FeSr₂Y_2-xCe_xCu₂O_10−δ with x = 0.3 and compared the results with previous measurements on a less hole doped sample with x = 0.7. We find that there is a spin-glass and the spin-glass temperature (~23 K) has not changed with hole doping from x = 0.7 to x = 0.3. The conduction mechanism is not affected by hole doping and it is still variable range hopping (VRH) for x = 0.3, which indicates that there is still considerable disorder from Cu and Fe antisite disorder as well as oxygen site disorder in the FeO_2-x planes. A large negative magnetoresistance of up to −10% is observed at 8 T but it is less than half of that reported for x = 0.7. The negative magnetoresistance can be accounted using the Nguen, Spivak, and Shklovskii (NSS) model where there is VRH quantum interference. The positive magnetoresistance at 2 K reported for x = 0.7 is not seen in x = 0.3 although the magnetoresistance becomes less negative below 5 K. A positive low temperature magnetoresistance can occur owing to scattering from free localised spins that is not accounted for in the NSS model and the difference in the low temperature magnetoresistance may be owing to a reduced concentration of localised free spins for x = 0.3 when compared with x = 0.7.

Keywords: iron cuprates; disordered systems; spin-glass temperature; hole doping; variable range hopping; VRH; magnetoresistance; electronic transport; magnetic properties; rare earth doping.

DOI: 10.1504/IJNT.2017.082482

International Journal of Nanotechnology, 2017 Vol.14 No.1/2/3/4/5/6, pp.367 - 374

Published online: 24 Feb 2017 *

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