Comparison of pressure, magnetic field and excess manganese effects on transport properties of film and bulk ceramic La–Ca manganites

• Published in: Физика низких температур
• Date: 2006
• Main Authors: Mikhaylov, V.I., Dyakonov, V.P., Zubov, E.E., Pashchenko, A.V., Varyukhin, V.N., Shtaba, V.A., Szewczyk, A., Abal’oshev, A., Piotrowski, K., Dyakonov, K., Lewandowski, S.J., Szymczak, H.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2006
• Subjects: Электpонные свойства металлов и сплавов
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/120130
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Comparison of pressure, magnetic field and excess manganese effects on transport properties of film and bulk ceramic La–Ca manganites / V.I. Mikhaylov, V.P. Dyakonov, E.E. Zubov, A.V. Pashchenko, V.N. Varyukhin, V.A. Shtaba, A. Szewczyk, A. Abal’oshev, K. Piotrowski, K. Dyakonov, S.J. Lewandowski, H. Szymczak // Физика низких температур. — 2006. — Т. 32, № 2. — С. 190-200. — Бібліогр.: 43 назв. — англ.

The pressure, magnetic field and excess manganese effects on transport and magnetoresistance
 effect (MRE) have been studied in both the epitaxial films and bulk ceramics of manganites
 (La₀.₇Ca₀.₃)₁₋xMn₁₊xO₃₋y (x = 0–0.2). A comparison of electrical behavior in both kinds of samples
 of similar composition at hydrostatic pressures of up to 1.8 GPa and in a magnetic fields of up
 to 8 kOe has been performed. The pressure and magnetic field effects are shown to increase with
 increasing manganese content. Experimental data show that the pressure and magnetic field effects
 on temperatures of both metal–insulator transition (TMD) and MRE peak (TMR) are considerably
 stronger in the films than in ceramics. The hydrostatic pressure increases TMD and TMR.
 Magnetoresistance effect for both types of samples was shown to be favored by the pressure and
 magnetic field in an opposite way. A direct correlation is established between TMD and conductivity
 bandwidth as well as between MRE and concentration of charge carriers at applied pressure.
 The differences in the values of pressure effect on resistance, MRE and TMD temperature in the
 films and ceramics are connected with both granular structure of ceramics and the oxygen
 nonstoichiometry in ceramic and film samples of the same content as well as with the film strain
 induced by lattice mismatch between the film and the substrate. The origin of pressure–magnetic
 field effects is analyzed in the framework of double exchange interaction and small polaron hopping,
 and variable range hopping models.