Grain-Size-Induced Collapse of Variable Range Hopping and Promotion of Ferromagnetism in Manganite La0.5Ca0.5MnO3

Crystals

Emil Tafra¹  Mario Basletić¹  Amir Hamzić¹  Željko Skoko¹  David Rivas Góngora²  Bojana Korin-Hamzić²  Tomislav Ivek²  Silvia Tomić²  Nikolina Novosel²  Matija Čulo²  Zvonko Jagličić³  Boris P. Gorshunov⁴  Teodoro Klaser⁵  Krešimir Salamon⁵  Tao Zhang⁶  Ivna Kavre Piltaver⁷  Mladen Petravić⁷ 

[1] Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia;Institut za fiziku, Bijenička cesta 46, HR-10000 Zagreb, Croatia;Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana, Slovenia;Laboratory of Terahertz Spectroscopy, Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, National Research University, 141701 Dolgoprudny, Russia;Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia;School of Physics and Materials Sciences, Guangzhou University, Guangzhou 510006, China;University of Rijeka, Faculty of Physics and Center for Micro- and Nanosciences and Technologies, Radmile Matejcic 2, 51000 Rijeka, Croatia;

关键词: manganites;    colossal magnetoresistance;    metal–insulator transition;    charge order;    grain size;    variable range hopping;   

DOI  :  10.3390/cryst12050724

来源: DOAJ

【 摘 要 】

Among transition metal oxides, manganites have attracted significant attention because of colossal magnetoresistance (CMR)—a magnetic field-induced metal–insulator transition close to the Curie temperature. CMR is closely related to the ferromagnetic (FM) metallic phase which strongly competes with the antiferromagnetic (AFM) charge ordered (CO) phase, where conducting electrons localize and create a long range order giving rise to insulator-like behavior. One of the major open questions in manganites is the exact origin of this insulating behavior. Here we report a dc resistivity and magnetization study on manganite La${}_{1-x}$Ca${}_x$MnO${}_3$ ceramic samples with different grain size, at the very boundary between CO/AFM insulating and FM metallic phases $x=0.5$. Clear signatures of variable range hopping (VRH) are discerned in resistivity, implying the disorder-induced (Anderson) localization of conducting electrons. A significant increase of disorder associated with the reduction in grain size, however, pushes the system in the opposite direction from the Anderson localization scenario, resulting in a drastic decrease of resistivity, collapse of the VRH, suppression of the CO/AFM phase and growth of an FM contribution. These contradictory results are interpreted within the standard core-shell model and recent theories of Anderson localization of interacting particles.

【 授权许可】

Unknown