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Metastable states in manganites - experimental aspects

Vladimir I. Markovich 

Ben-Gurion University of the Negev, P.O.Box 653, Beer-Sheva 84105, Israel


The spin, charge, lattice and orbital degrees of freedom in doped manganites are strongly coupled to each other, leading to rich phase diagram with a variety of competing phases. External stimuli such as electric current/field may affect the topology of coexisting phases, leading to difference between transport properties of various metastable resistive states (MRS) in the same sample. MRS in La1-xCaxMnO3 (x=0.18,0.2) crystals can be created by a current treatment. They are characterized by long-term memory surviving even thermal cycling to room temperature. Only heating to T>350 K erases the imprinted state of the system. The nature of phase competition can be understood in terms of glass like transition at low temperatures and to the appearance of Griffith-phase regime at temperatures TC<T<TG, where TC and TG are the Curie and Griffith temperatures, respectively.

In the pristine state polycrystalline Sm0.1Ca0.84Sr0.06MnO3 exhibits phase separation below TC=105 K comprising ferromagnetic (FM) and antiferromagnetic phases. The metastable states with reduced magnetization or diamagnetic (DIA) response were obtained by successive number of quick cooling of the sample placed in container with kerosene-oil mixture. The observed field and temperature dependences of the magnetization in DIA state are reversed in comparison with ordinary FM ones. Only after some storage time at room temperature, the abnormal magnetic state is erasable. It seems plausible that localized electron orbits with radius of tens nanometers, confined within dislocation network, may give rise to the DIA effects at temperatures 105 K<T<240 K. At T<105 K the magnetic response to external magnetic field is controlled mainly by the coupling of FM clusters with DIA matrix.


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Presentation: Invited oral at E-MRS Fall Meeting 2006, Symposium K, by Vladimir I. Markovich
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-07 11:18
Revised:   2009-06-07 00:44