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Article

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

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Institut za fiziku, Bijenička cesta 46, HR-10000 Zagreb, Croatia
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Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana, Slovenia
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Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova c. 2, 1000 Ljubljana, Slovenia
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Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia
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Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
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University of Rijeka, Faculty of Physics and Center for Micro- and Nanosciences and Technologies, Radmile Matejcic 2, 51000 Rijeka, Croatia
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Laboratory of Terahertz Spectroscopy, Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, National Research University, 141701 Dolgoprudny, Russia
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School of Physics and Materials Sciences, Guangzhou University, Guangzhou 510006, China
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Current address: Department of Physics, University of Oslo, NO-0316 Oslo, Norway.
Academic Editors: Raghvendra Singh Yadav and Artem Pronin
Crystals 2022, 12(5), 724; https://doi.org/10.3390/cryst12050724
Received: 16 April 2022 / Revised: 13 May 2022 / Accepted: 16 May 2022 / Published: 19 May 2022
(This article belongs to the Special Issue New Spin on Metal-Insulator Transitions)
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 La1xCaxMnO3 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. View Full-Text
Keywords: manganites; colossal magnetoresistance; metal–insulator transition; charge order; grain size; variable range hopping; Anderson localization; core–shell model manganites; colossal magnetoresistance; metal–insulator transition; charge order; grain size; variable range hopping; Anderson localization; core–shell model
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MDPI and ACS Style

Novosel, N.; Rivas Góngora, D.; Jagličić, Z.; Tafra, E.; Basletić, M.; Hamzić, A.; Klaser, T.; Skoko, Ž.; Salamon, K.; Kavre Piltaver, I.; Petravić, M.; Korin-Hamzić, B.; Tomić, S.; Gorshunov, B.P.; Zhang, T.; Ivek, T.; Čulo, M. Grain-Size-Induced Collapse of Variable Range Hopping and Promotion of Ferromagnetism in Manganite La0.5Ca0.5MnO3. Crystals 2022, 12, 724. https://doi.org/10.3390/cryst12050724

AMA Style

Novosel N, Rivas Góngora D, Jagličić Z, Tafra E, Basletić M, Hamzić A, Klaser T, Skoko Ž, Salamon K, Kavre Piltaver I, Petravić M, Korin-Hamzić B, Tomić S, Gorshunov BP, Zhang T, Ivek T, Čulo M. Grain-Size-Induced Collapse of Variable Range Hopping and Promotion of Ferromagnetism in Manganite La0.5Ca0.5MnO3. Crystals. 2022; 12(5):724. https://doi.org/10.3390/cryst12050724

Chicago/Turabian Style

Novosel, Nikolina, David Rivas Góngora, Zvonko Jagličić, Emil Tafra, Mario Basletić, Amir Hamzić, Teodoro Klaser, Željko Skoko, Krešimir Salamon, Ivna Kavre Piltaver, Mladen Petravić, Bojana Korin-Hamzić, Silvia Tomić, Boris P. Gorshunov, Tao Zhang, Tomislav Ivek, and Matija Čulo. 2022. "Grain-Size-Induced Collapse of Variable Range Hopping and Promotion of Ferromagnetism in Manganite La0.5Ca0.5MnO3" Crystals 12, no. 5: 724. https://doi.org/10.3390/cryst12050724

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