| Full text | |
| Author(s): |
Mardegan, J. R. L.
;
Fabbris, G.
;
Veiga, L. S. I.
;
Adriano, C.
;
Avila, M. A.
;
Haskel, D.
;
Giles, C.
Total Authors: 7
|
| Document type: | Journal article |
| Source: | PHYSICAL REVIEW B; v. 88, n. 14, p. 8-pg., 2013-10-16. |
| Abstract | |
We investigate the low temperature structural and electronic properties of the type-I clathrate Eu8Ga16Ge30 under pressure using x-ray powder diffraction (XRD), x-ray absorption near-edge structure (XANES), and x-ray magnetic circular dichroism (XMCD) techniques. The XRD measurements reveal a transition to an amorphous phase above 18 GPa. Unlike previous reports on other clathrate compounds, no volume collapse is observed prior to the crystalline-amorphous phase transition which takes place when the unit cell volume is reduced to 81% of its ambient pressure value. Fits of the pressure-dependent relative volume to a Murnaghan equation of state yield a bulk modulus B-0 = 65 +/- 3 GPa and a pressure derivative B '(0) = 3.3 +/- 0.5. The Eu L2-edge XMCD data shows quenching of the magnetic order at a pressure coincident with the crystalline-amorphous phase transition. This information along with the persistence of an Eu2+ valence state observed in the XANES spectra up to the highest pressure point (22 GPa) indicates that the suppression of XMCD intensity is due to the loss of long range magnetic order. When compared with other clathrates, the results point to the importance of guest ion-cage interactions in determining the mechanical stability of the framework structure and the critical pressure for amorphization. Finally, the crystalline structure is not found to recover after pressure release, resulting in an amorphous material that is at least metastable at ambient pressure and temperature. (AU) | |
| FAPESP's process: | 12/17562-9 - Preparation of oriented single crystals for studies on electronic, magnetic and thermal anisotropies |
| Grantee: | Marcos de Abreu Avila |
| Support Opportunities: | Regular Research Grants |
| FAPESP's process: | 09/10264-0 - Study of intermetalic compounds for thermoelectrical applications by x-ray diffraction |
| Grantee: | José Renato Linares Mardegan |
| Support Opportunities: | Scholarships in Brazil - Doctorate |
| FAPESP's process: | 12/10675-2 - Probing the magnetization dynamics of antiferromagnetic NiO by time resolved X-ray magnetic scattering |
| Grantee: | Carlos Manuel Giles Antunez de Mayolo |
| Support Opportunities: | Scholarships abroad - Research |
| FAPESP's process: | 11/24166-0 - Study of intermetallic compounds using synchrotron radiation spectroscopy |
| Grantee: | José Renato Linares Mardegan |
| Support Opportunities: | Scholarships abroad - Research Internship - Doctorate |