Reentrant Superspin Glass Phase in a La0.82Ca0.18MnO3 Ferromagnetic Insulator

• Published in: Physical review. X Vol. 4; no. 1; p. 011037
• Main Authors: P. Anil Kumar, Mathieu, R, Nordblad, P, Ray, Sugata, Karis, Olof, Andersson, Gabriella, Sarma, D D
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 2014
• Subjects: Antiferromagnetism; Calcium; Current carriers; Dipole moments; Electron transport; Engineering Science with specialization in Solid State Physics; Ferromagnetic phases; Ferromagnetism; Insulation; Lanthanum compounds; Long range order; Magnetic dipoles; Magnetic induction; Magnetic moments; Magnetic relaxation; Magnetism; Magnetization; Manganese; Manganites; Metal compounds; Metallicity; Perovskites; Phase diagrams; Phase transitions; Single crystals; Teknisk fysik med inriktning mot fasta tillståndets fysik; Transition metal compounds
• ISSN: 2160-3308; 2160-3308
• DOI: 10.1103/PhysRevX.4.011037

We report results of the magnetization and ac susceptibility measurements down to very low fields on a single crystal of the perovskite manganite, La0.82Ca0.18MnO3 . This composition falls in the intriguing ferromagnetic insulator region of the manganite phase diagram. In contrast to earlier beliefs, our investigations reveal that magnetically (and in every other sense), this is a single-phase system with a ferromagnetic ordering temperature of around 170 K. However, this ferromagnetic state is magnetically frustrated, and the system exhibits pronounced glassy dynamics below 90 K. Based on measured dynamical properties, we propose that this quasi-long-ranged ferromagnetic phase, and the associated superspin glass behavior, is the true magnetic state of the system, rather than being a macroscopic mixture of ferromagnetic and antiferromagnetic phases, as often suggested. Our results provide an understanding of the quantum phase transition from an antiferromagnetic insulator to a ferromagnetic metal via this ferromagnetic insulating state as a function of x in La1−xCaxMnO3 , in terms of the possible formation of magnetic polarons.