Magnetotransport in epitaxial thin films of the magnetic perovskitePr0.5Sr0.5

Abstract

Thin, c ជ -axis oriented films of the magnetic perovskite Pr 0.5 Sr 0.5 MnO 3 were prepared by dc-magnetron sputtering, structurally characterized by x-ray diffraction and their physical properties investigated by magnetization and electrical transport measurements. Ferromagnetic ordering appears in zero field at 263 K, followed by a second transition into an antiferromagnetic state at 160 K. The zero-field resistivity has a semiconducting behavior above the Curie and below the Néel temperature and is analyzed in the framework of Mott's variable range hopping concept. Quasimetallic behavior is observed within the ferromagnetic state, whose temperature range can be extended by applying an external magnetic field. The negative magnetoresistance effect increases systematically with decreasing temperature and reaches a value of 700% at 1.5 K in a field of 12 T. In the ferro-and antiferromagnetic phases, the field induced resistivity decrease scales with the Brillouin function, suggesting the existence of magnetically polarized regions with a total magnetic moment which is reduced upon entering the antiferromagnetic state.

Non-adiabatic small polaron hopping in then= 3 Ruddlesden–Popper compound Ca4Mn3O10

“…Quantitatively, a model that accounts for the MR in manganites based on activated hopping with additional barriers due to magnetic misalignment of the local moments has been developed by Wagner and co-workers, who expressed the new activation barrier as 51,52 ( )…”

“…51,52 for a formal development of the model). Given that the application of an external magnetic field does not affect the term W ij , the drop in resistivity (i.e.…”

Magnetic localization in mixed-valence manganites

“…13,17,18 We have measured resistivity vs temperature characteristics for a wide range of samples which exhibit a metal-insulator transition. The T Ϫ1 law, which would be characteristic of nearest-neighbor hopping or activation to a mobility edge, does not fit the data.…”

Pressure-induced electrical and magnetic property changes in CaCuMn6O12

“…As a highly correlated electron system, at low temperature (45 K < T < 100 K), CaCuMn 6 O 12 has a small gap appearing at E F because the resistivity is in accordance with Mott's law for variable range hopping and the hopping law is log(ρ)∝(1/T) 1/2 [12]. At high temperature (T > 100 K), the carriers form small dielectric polarons and the temperature dependence of resistivity follows thermally activated nearest-neighbor hopping, i.e., log(ρ)∝(1/T) [13]. The exact turning point of two parts was determined as 113.3 K through anatomizing the inset of Fig.…”