Experimental evidence for a magnetic two-phase state in manganites

It is found that samples of manganites La0.9Sr0.1MnO3 (single crystal), Eu(0.7)A(0.3)MnO(3) (A = Ca, Sr; ceramics), and La0.1Pr0.6Ca0.3MnO3 and La0.84Sr0.16MnO3 (thin epitaxial films) that are either field-cooled (in a magnetic field) or zero-field-cooled differ in low-temperature magnetization, and the hysteresis loop of field-cooled samples exhibits a displacement. This displacement signifies that a ferro-antiferromagnetic state occurs in these samples. The exchange integral J similar to 10(-6) eV is calculated from this displacement, which describes the exchange Mn-O-Mn coupling through the interface ferromagnetic droplet-antiferromagnetic matrix. The magnetoresistance and volume magnetostriction of La1 - xSrxMnO3 single crystals exhibit similar dependences on x, temperature, and the magnetic field in the vicinity of the Curie point, which points to the fact that these dependences are due to the same reason, namely, the occurrence of a magnetic two-phase ferro-antiferromagnetic state caused by strong s-d exchange. (C) 2002 MAIK "Nauka / Interperiodica".