Abstract
Magnetic compounds with significant and temperature-insensitive magnetoresistance are quite promising for device applications. Here, we intentionally doped different amounts (0.025-0.1) of Co into epitaxial (La0.7Sr0.3)MnO3 thin films. The evolution of electrical, magnetic, magneto-transport, and valence state of this series of Co-doped (La0.7Sr0.3)MnO3 have been systematically characterized. Remarkably, the magnetoresistance in 0.1Co-doped (La0.7Sr0.3)MnO3 can reach significantly 35% within an extremely large temperature window (from 40 to 200 K). Other Co-doped epitaxial (La0.7Sr0.3)MnO3 thin films show similar sharp MR-peaks around Curie temperature as that in (La0.7Sr0.3)MnO3. The evolution of magnetic and magneto-transport properties of Co-(La0.7Sr0.3)MnO3 films can be explained by antiferromagnetic coupling induced by paramagnetic/low-spin Co3+(Co2+) ions in (La0.7Sr0.3)MnO3. Our work demonstrates that doping paramagnetic/low-spin Co into manganites is an effective way to optimize their magneto-transport properties.
Highlights
INTRODUCTIONPerovskite Ln1-xAxMnO3 manganites (where Ln and A are lanthanides and alkaline-earth elements, respectively) have attracted much attention for decades due to their intriguing physical properties (for example colossal magnetoresistance (CMR), metal-insulator transition, spin/charge/orbital ordering) and the resulting applications in electrical devices. These properties can be attributed to strong correlation between magnetism and electrical conductivity therein
Extensive works are applied to B-sitetransition-metal-doped (La,Sr)MnO3 (LSMO) that demonstrate complex magnetic states, such as FM/AFM coupling induced competing interaction and resultant spin glass behavior in Cr-doped La0.46Sr0.54Mn1-xCrxO3,12 relaxor ferromagnet in Nd0.5Ca0.5Mn1-xCrxO3.13 Among them, Co-doped LSMO show quite unique properties and potential applications, such as significant magnetic and magneto-caloric properties coming from complex spin-states in Co,14,15 large exchange bias in Co-doped LSMO,16,17 candidate as the cathode material in solid-oxide fuel cells,18 and enhanced ferromagnetism in Co-doped La0.45Sr0.55MnO3.19–22
Based on valence state characterization, the large and temperature-insensitive MR observed in 0.1Co-doped LSMO is tentatively attributed to that 0.1 Co atomic concentration might be a critical value of the boundary between spin glass and long-range ferromagnetic order
Summary
Perovskite Ln1-xAxMnO3 manganites (where Ln and A are lanthanides and alkaline-earth elements, respectively) have attracted much attention for decades due to their intriguing physical properties (for example colossal magnetoresistance (CMR), metal-insulator transition, spin/charge/orbital ordering) and the resulting applications in electrical devices. These properties can be attributed to strong correlation between magnetism and electrical conductivity therein.. Perovskite Ln1-xAxMnO3 manganites (where Ln and A are lanthanides and alkaline-earth elements, respectively) have attracted much attention for decades due to their intriguing physical properties (for example colossal magnetoresistance (CMR), metal-insulator transition, spin/charge/orbital ordering) and the resulting applications in electrical devices.. Perovskite Ln1-xAxMnO3 manganites (where Ln and A are lanthanides and alkaline-earth elements, respectively) have attracted much attention for decades due to their intriguing physical properties (for example colossal magnetoresistance (CMR), metal-insulator transition, spin/charge/orbital ordering) and the resulting applications in electrical devices.1–8 These properties can be attributed to strong correlation between magnetism and electrical conductivity therein.. Poor crystalline quality maybe covers the their intrinsic physical property In light of these considerations, we grew a series of Codoped LSMO (hereafter LSMO represents (La0.7Sr0.3)MnO3) on (001) STO substrates and systematically investigate their structures, magnetic and electric transport properties. Based on valence state characterization, the large and temperature-insensitive MR observed in 0.1Co-doped LSMO is tentatively attributed to that 0.1 Co atomic concentration might be a critical value of the boundary between spin glass and long-range ferromagnetic order
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