Effect of Ising-type Tb$^{3+}$ ions on the low-temperature magnetism of La, Ca cobaltite
| Autor: | Knížek, K., Jirák, Z., Hejtmánek, J., Veverka, M., Kaman, O., Maryško, M., Šantavá, E., André, G. |
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| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | J. Phys.-Condens. Mat. 26, 116003 (2014) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1088/0953-8984/26/11/116003 |
| Popis: | Crystal and magnetic structures of the $x=0.2$ member of La$_{\rm 0.8-x}$Tb$_{\rm x}$Ca$_{0.2}$CoO$_3$ perovskite series have been determined from the powder neutron diffraction. Enhancement of the diffraction peaks due to ferromagnetic or cluster glass ordering is observed below $T_C=55$ K. The moments evolve at first on Co sites, and ordering of Ising-type Tb$^{3+}$ moments is induced at lower temperatures by a molecular field due to Co ions. The final magnetic configuration is collinear F$_x$ for cobalt subsystem, while it is canted F$_x$C$_y$ for terbium ions. The rare-earth moments align along local Ising axes within \textit{ab}-plane of the orthorhombic $Pbnm$ structure. The behavior in external fields up to $70-90$ kOe has been probed by the magnetization and heat capacity measurements. The dilute terbium ions contribute to significant coercivity and remanence that both steeply increase with decreasing temperature. A remarkable manifestation of the Tb$^{3+}$ Ising character is the observation of a low-temperature region of anomalously large linear term of heat capacity and its field dependence. Similar behaviours are detected also for other terbium dopings $x=0.1$ and 0.3. Comment: 8 pages, 11 figures |
| Databáze: | arXiv |
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