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Title: Anomalous specific heat and magnetic properties of Tm xDy 1-xAl 2 (0 ≤ x ≤ 1)

Abstract

Here, we study crystal structure, phase transitions and magnetism of pseudo-binary Tm xDy 1-xAl 2 (0 ≤ x ≤ 1) compounds using temperature dependent X-ray powder diffraction, specific heat and magnetization measurements, first principles, and model calculations. In low external magnetic fields, Dy-rich compounds undergo continuous, second-order phase transitions at the respective Curie temperatures, T C. In contrast, the Tm-rich compounds exhibit discontinuous, first-order anomalies in the magnetically ordered states. These sharp transitions correlate with a substantial energy difference between the room temperature cubic and ground state rhombohedral structures of TmAl 2. A clear anomaly in the lattice parameter is observed at ~30 K for x = 0.5, which nearly coincides with T C = 31.2 K. The effective quadrupolar moment of the lanthanides changes sign around x = 0.5, which leads to a nearly zero anisotropy constant and approximately spherical effective 4f charge densities, providing an explanation for the lack of structural distortions below T C for x = 0.5. The calculations confirm [001] as the easy magnetization axis in the ground state tetragonal structure of DyAl 2, and reveal collapse of the orbital magnetic moment when the easy magnetization direction changes to [111]. Within the rhombohedral ground statemore » of TmAl 2 [111] is the easy magnetization direction.« less

Authors:
ORCiD logo [1];  [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1478989
Report Number(s):
IS-J-9785
Journal ID: ISSN 0925-8388; PII: S0925838818336302
Grant/Contract Number:  
AC02-07CH11358
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Alloys and Compounds
Additional Journal Information:
Journal Volume: 774; Journal Issue: C; Journal ID: ISSN 0925-8388
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Specific heat; Rare earth; First-order-phase-transition; Lanthanoids

Citation Formats

Pathak, Arjun K., Bonilla, C. M., Paudyal, D., Mudryk, Y., and Pecharsky, V. K. Anomalous specific heat and magnetic properties of TmxDy1-xAl2 (0 ≤ x ≤ 1). United States: N. p., 2018. Web. doi:10.1016/j.jallcom.2018.09.365.
Pathak, Arjun K., Bonilla, C. M., Paudyal, D., Mudryk, Y., & Pecharsky, V. K. Anomalous specific heat and magnetic properties of TmxDy1-xAl2 (0 ≤ x ≤ 1). United States. doi:10.1016/j.jallcom.2018.09.365.
Pathak, Arjun K., Bonilla, C. M., Paudyal, D., Mudryk, Y., and Pecharsky, V. K. Fri . "Anomalous specific heat and magnetic properties of TmxDy1-xAl2 (0 ≤ x ≤ 1)". United States. doi:10.1016/j.jallcom.2018.09.365. https://www.osti.gov/servlets/purl/1478989.
@article{osti_1478989,
title = {Anomalous specific heat and magnetic properties of TmxDy1-xAl2 (0 ≤ x ≤ 1)},
author = {Pathak, Arjun K. and Bonilla, C. M. and Paudyal, D. and Mudryk, Y. and Pecharsky, V. K.},
abstractNote = {Here, we study crystal structure, phase transitions and magnetism of pseudo-binary TmxDy1-xAl2 (0 ≤ x ≤ 1) compounds using temperature dependent X-ray powder diffraction, specific heat and magnetization measurements, first principles, and model calculations. In low external magnetic fields, Dy-rich compounds undergo continuous, second-order phase transitions at the respective Curie temperatures, TC. In contrast, the Tm-rich compounds exhibit discontinuous, first-order anomalies in the magnetically ordered states. These sharp transitions correlate with a substantial energy difference between the room temperature cubic and ground state rhombohedral structures of TmAl2. A clear anomaly in the lattice parameter is observed at ~30 K for x = 0.5, which nearly coincides with TC = 31.2 K. The effective quadrupolar moment of the lanthanides changes sign around x = 0.5, which leads to a nearly zero anisotropy constant and approximately spherical effective 4f charge densities, providing an explanation for the lack of structural distortions below TC for x = 0.5. The calculations confirm [001] as the easy magnetization axis in the ground state tetragonal structure of DyAl2, and reveal collapse of the orbital magnetic moment when the easy magnetization direction changes to [111]. Within the rhombohedral ground state of TmAl2 [111] is the easy magnetization direction.},
doi = {10.1016/j.jallcom.2018.09.365},
journal = {Journal of Alloys and Compounds},
number = C,
volume = 774,
place = {United States},
year = {2018},
month = {9}
}

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