EPR study of Gd{sup 3+}-doped RbR(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O (R=Pr,Nd,Sm,Eu) single crystals: Phase transitions and spin-Hamiltonian parameters

Journal Article · Fri Aug 01 00:00:00 EDT 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.2391· OSTI ID:548794

Misra, S K ^[1]; Misiak, L E ^[1]

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1. Department of Physics, Concordia University, 1455 de Maisonneuve Boulevard West, Montreal, Quebec, H3G 1M8 (CANADA)

Extensive EPR measurements were carried out in the temperature range 100{endash}300 K. The room-temperature data indicate that Gd{sup 3+} ions substitute equally for R{sup 3+} ions at the two magnetically inequivalent sites in the unit cell, and that the site symmetry of the Gd{sup 3+} ion is monoclinic. The Gd{sup 3+} room-temperature spin-Hamiltonian parameters and linewidths were estimated. The phase transition temperatures (T{sub c}) were determined to be 175{plus_minus}1K (first order) in RbPr(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, 178.5{plus_minus}1K (first order) in RbNd(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, 232{plus_minus}0.5K (second order) in RbSm(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, and 230.5{plus_minus}0.5K (second order) in RbEu(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O. In RbPr(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O and RbNd(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O, the occurrence of the first-order phase transitions was deduced from abrupt changes in the behavior of the linewidth, zero-field splitting, and line positions, and coexistence of lines observed below and above T{sub c}. In addition, there were observed occurrences of two more phase transitions second order in nature in RbPr(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O (T{sub c1}=261K, T{sub c2}=207.5K) and in RbNd(SO{sub 4}){sub 2}{center_dot}4H{sub 2}O (T{sub c1}=250K, T{sub c2}=219.5K); these were not as sharply defined as the preceding ones. Below T{sub c}, for all the crystals, the symmetry of the crystals was found to be lower than monoclinic, the four ions in the unit cell becoming magnetically inequivalent from each other. The observed second-order phase transitions in the four crystals were found to be in agreement with Landau theory of second-order phase transitions; the critical exponent was determined to be {beta}{congruent}0.51. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 548794
• Journal Information: Physical Review, B: Condensed Matter, Vol. 56, Issue 5; Other Information: PBD: Aug 1997
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
GADOLINIUM IONS
ELECTRON SPIN RESONANCE
RUBIDIUM COMPOUNDS
CRYSTAL-PHASE TRANSFORMATIONS
PRASEODYMIUM SULFATES
NEODYMIUM SULFATES
SAMARIUM COMPOUNDS
EUROPIUM COMPOUNDS
DOPED MATERIALS
SPIN
HAMILTONIANS
WATER
TRANSITION TEMPERATURE
MAGNETIC PROPERTIES
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K