Milan Klicpera: Spin-glass ground-state in Er2Zr2O7: the case of magnetic correlations on diluted fcc lattice
Venue: Ke Karlovu 5, Prague 2
We have a pleasure to invite you to attend the joint seminar
of the Department of Condensed Matter Physics (DCMP)
and the Materials Growth and Measurement Laboratory (MGML) http://mgml.eu.
Spin-glass ground-state in Er2Zr2O7: the case of magnetic correlations on diluted fcc lattice
lecture given by:
Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Prague 2, Czech Republic
The seminar takes place in the lecture room F2
of the Faculty of Mathematics and Physics, Ke Karlovu 5, Praha 2
on Wednesday, 27.11. 2019 from 14:10
On behalf of the DCMP and MGML
Cubic A2B2O7 oxides with A standing for a rare-earth element and B for a transition or main block metal have been systematically studied for their frequently exotic crystallographic and electronic properties. Diverse ground states, magnetic structures and predicted exciting electronic, magnetic and even topological properties originating from a competition between electron-electron correlations and spin-orbit coupling have been reported [1 and references therein]. The geometrical frustration of magnetic moments residing on the A and/or B crystallographic positions offer a playground for scientific investigations as well.
A2B2O7 compounds in general crystallize either in a pyrochlore structure (F d -3 m, 227), defect-fluorite structure (F m -3 m, 225) or a low-symmetry monoclinic structure (P 1 1 21, 2 ) at ambient pressure. The pyrochlore structure represents one of the canonical examples for a structure where a unique ground state is difficult to achieve for a system of magnetically coupled moments as demonstrated on a number of compounds [1,3,4 and references therein]. The fluorite structure is another example of a geometrically frustrated lattice, due to the fcc lattice of cations. However, the rare-earth/transition metal octahedra are edge-, not vertex- sharing leading to a different exchange pathway type and thus different magnetic exchanges. Moreover, the diluted magnetic lattice (complete A/B disorder on the 4a position) is bound to have a great impact on the ground state of A2B2O7 compounds as well.
We present our recent results on Er2Zr2O7 crystallizing in defect-fluorite structure and Er2Ir2O7 adopting pyrochlore structure. Former compound was prepared as a single crystal for the first time, being concurrently the first single crystal in the A2Zr2O7 family adopting the defect-fluorite type of cubic structure. The single crystal was characterized by x-ray and neutron diffraction methods and studied by means of magnetization, AC- susceptibility and specific heat . Simultaneously, basic physical properties of Er2Ir2O7 polycrystal were studied. The bulk data are well in agreement with microscopic study (neutron diffraction (GEM, ISIS), low- temperature (0.3 K) neutron diffraction experiment (E6, HZB) and inelastic neutron scattering experiment (MARI, ISIS)). New results on Er2T2O7 and future plans on study of other rare-earth zirconates and iridates will be discussed in broader context of RE2T2O7 family.
 W. Witczak-Krempa, G. Chen, Y. B. Kim, L. Balents, Annu. Rev. Condens. Matter Phys. 5, 57–82 (2014).
 N. Ishizawa, K. Ninomiya, T. Sakakura, J. Wang, Acta Crystall. E69, 19 (2013).
 M.J.P. Gingras, C.V. Stager, N.P. Raju, B.D. Gaulin, J.E. Greedan, Phys. Rev. Lett. 78, 947-950 (1997).
 J.-J. Wen, S.M. Koohpayeh, K.A. Ross, B.A. Trump, T.M. McQueen, K. Kimura, S. Nakatsuji, Y. Qiu, D.M. Pajerowski, J.R.D. Copley, C.L. Broholm, Phys. Rev. Lett. 118, 107206 (2017).
 K. Vlášková, R.H. Colman, P. Proschek, J. Čapek, M. Klicpera, submitted to Phys. Rev. B.
- Wednesday, 27 November 2019 14:10 - 15:10