Tracking and understanding the first-order structural transition in Er5Si4

Date
2004-01-01
Authors
Mozharivskyj, Yurij
Pecharsky, Alexandra
Pecharsky, Vitalij
Miller, Gordon
Gschneidner, Karl
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Ames Laboratory
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Chemistry
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Abstract

Temperature-dependent single crystal x-ray-diffraction studies revealed a reversible first-order phase transition in Er5Si4. The high-temperature phase adopts the orthorhombic Gd5Si4-type structure, and the low-temperature phase has the monoclinic Gd5Si2Ge2-type structure. Unlike the magnetic/martensitic transition in Gd5Si2Ge2, the structural change in Er5Si4 is not coupled with a magnetic transition, and the structural sequence below room temperature is just the reverse. A vibrational mode that breaks half of the interslab silicon dimers and rotates slabs in the monoclinic structure, thus lowering the symmetry from Pnma to P1121/a, has been identified using Landau theory. While the monoclinic phase is electronically stabilized at low temperatures, the orthorhombic phase is entropically preferable at high temperatures.

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This article is from Physical Review B 69 (2004): 1, doi:10.1103/PhysRevB.69.144102. Posted with permission.

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