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We have studied the magnetic and magnetotransport properties of oxygen deficient R{sub 0.67}Sr{sub 0.33}MnO{sub {ital z}} (R=Nd, Pr) films and have observed superparamagnetic behavior in these films. The superparamagnetism is indicated by (i) the increasing spread between zero field cooled (ZFC) and field cooled (FC) magnetization curves as temperature decreases, (ii) a sharp drop of the ZFC magnetization at low temperature, (iii) enhanced Curie{endash}Weiss constant above the ferromagnetic temperature, and (iv) at low temperature a sharp drop of coercivity (H{sub {ital c}}) with increasing temperature. These findings strongly suggest that all oxygen deficient manganites are magnetically inhomogeneous; i.e., ferromagnetic clusters exist. We estimate the spin cluster diameter to be 7{endash}10 nm at low temperature ({ital T}{lt}30 K). We discuss a possible origin of the giant magnetoresistance effect based on the existence of spin clusters. {copyright} {ital 1996 American Institute of Physics.}
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| Authors: |
Ju, H.L.;
Li, Q.;
Xiong, G.C.;
Venkatesan, T.;
Greene, R.L. [Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)]
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| Publication Date: | 1996 Apr 01 |
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| OSTI Identifier: | 279992 |
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| Report Number(s): | CONF-951101-- |
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| Resource Type: | Journal Article |
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| Resource Relation: | Journal Name: Journal of Applied Physics; Journal Volume: 79; Journal Issue: 8; Conference: 40. conference on magnetism and magnetic materials, Philadelphia, PA (United States), 6-9 Nov 1995; Other Information: PBD: Apr 1996 |
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| Country of Publication: | United States |
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| Language: | English |
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| Format: | Size: pp. 4552 |
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| Other Number(s): | Journal ID: JAPIAU; ISSN 0021-8979; TRN: 96:018931 |
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| Subject: | 36 MATERIALS SCIENCE; NEODYMIUM OXIDES; MAGNETORESISTANCE; PRASEODYMIUM OXIDES; STRONTIUM OXIDES; MANGANESE OXIDES; FILMS; EPITAXY; SUPERPARAMAGNETISM; COERCIVE FORCE; SUBSTOICHIOMETRY; TEMPERATURE DEPENDENCE |
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| Related Subject: | SUBSTITUTION;MAGNETIC STRUCTURE |
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| Update Date: | 2009 Dec 16 |
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