- Jiří Pospíšil: UIrGe-antiferromagnetic counterpart of FM SC; effect of external variables
- 26. 4. 2017, 14:30
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
Particularly interesting are uranium compounds located close to the empirical Hill criterion1 which defines the limit of nearest uranium ions distance dU-U = 3.5 Å where 5f electrons change from localized to itinerant character. Then, external variables such as hydrostatic pressure or alloying are very effective tools for tuning the electronic state of the uranium ion. Isostructural compounds URhGe and UCoGe crystallizing in the TiNiSi-type structure naturally fulfil this condition and coexistence of FM and SC was discovered here2, 3.
We focused on another candidate UIrGe. Its importance has been highlighted by systematic study of the magnetic and structural parameters of the isostructural UTGe compounds4. UIrGe is an antiferromagnet (AFM) with Néel temperature TN = 16.5 K5, unlike the FMs UCoGe and URhGe. We employed pressure, high magnetic field and alloying to investigate the magnetic properties and potential quantum critical phenomena in this compound.
We have studied UIr1-xRhxGe system which has an interesting FM/AFM boundary at low temperature. This AFM/FM boundary is of interest because the AFM and FM are separated at this point throughout the whole orthorhombic TiNiSi-type UTGe system by the Hill limit4. Our single crystal study has allowed us to develop a general picture of the magnetism in the AFM part of the UIr1-xRhxGe system which surprisingly preserves many of the magnetic features of the FM parent compounds URhGe and UCoGe6. Our discussion and conclusions are based on a detailed analysis of the crystal structure, magnetization and heat capacity. Surprisingly, p-T phase diagram of UIrGe compound was not established. Our results of a series of high pressure experiments in two types of pressure cells using what appear to be the best available UIrGe single crystals will be presented. We have constructed a p-T phase diagram and estimated the critical pressure pc, where the AFM vanishes, as ~ 12 GPa. The AFM/paramagnetic transition appears to be first order. We suggest a scenario of competing AFM inter J- and FM intra J*-chain interactions in UIrGe. A moderate enhancement of the effective electron mass was detected in the vicinity of pc. We surmise that UIrGe may be a candidate for the SC state to potentially develop7.
1 H.H.Hill, Plutonium 1970 and Other Actinides (ed. W. N.Miner, (American Institute of Mining, Metalurgical, and Petroleum Engeneers, New York, 1970), p. 2, 1970).
2 D. Aoki, A. Huxley, E. Ressouche, D. Braithwaite, J. Flouquet, J. P. Brison, E. Lhotel, and C. Paulsen, Nature 413, 613 (2001).
3 N. T. Huy, A. Gasparini, D. E. de Nijs, Y. Huang, J. C. P. Klaasse, T. Gortenmulder, A. de Visser, A. Hamann, T. Gorlach, and H. von Löhneysen, Physical Review Letters 99, 067006 (2007).
4 M. Vališka, J. Pospíšil, M. Diviš, J. Prokleška, V. Sechovský, and M. M. Abd-Elmeguid, Physical Review B 92, 045114 (2015).
5 A. P. Ramirez, B. Batlogg, and E. Bucher, Journal of Applied Physics 61, 3189 (1987).
6 J. Pospíšil, Y. Haga, S. Kambe, Y. Tokunaga, N. Tateiwa, D. Aoki, F. Honda, A. Nakamura, Y. Homma, E. Yamamoto, and T. Yamamura, Physical Review B (accepted) (arXiv:1704.04013).
7 J. Pospíšil, J. Gouchi, Y. Haga, F. Honda, Y. Uwatoko, N. Tateiwa, S. Kambe, S. Nagasaki, Y. Homma, and E. Yamamoto, Journal of the Physical Society of Japan 86, 044709 (2017).