A MuSR study of the magnetoresistive ruthenocuprates RuSr2Nd1.8-xY0.2CexCu2O_{10-\delta} (x = 0.95 and 0.80)

Abstract

Zero field muon spin relaxation (ZF-{\mu}SR) has been used to study the magnetic properties of the underdoped giant magnetoresistive ruthenocuprates (GMR) RuSr2Nd1.8-xY0.2CexCu2O10-d (x = 0.95, 0.80). The results show a gradual loss of initial asymmetry A0 at the ruthenium spin transition temperature, TRu. At the same time the electronic relaxation rate, lambda shows a gradual increase with decreasing temperature below TRu. These results have been interpreted as evidence for Cu spin cluster formation below TRu. These magnetically ordered clusters grow as the temperature is decreased thus causing the initial asymmetry to decrease slowly. GMR is observed over a wide temperature range in the materials studied and the magnitude increases as the temperature is reduced from TRu to 4 K which suggests a relation between Cu spin cluster size and -MR.