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| Author(s): |
Denise Sacramento Christovam
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin |
| Defense date: | 2020-10-09 |
| Examining board members: |
Pascoal José Giglio Pagliuso;
Eduardo Miranda;
Priscila Ferrari Silveira Rosa
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| Advisor: | Pascoal José Giglio Pagliuso |
| Abstract | |
The interplay between magnetism and unconventional superconductivity in strongly correlated systems remains one of the most interesting topics in condensed matter physics to be unveiled. The emergence of such states is commonly found among the heavy-fermion materials, and some of the most prominent examples are the CemMnIn3m+2n (M = Co, Rh, Ir; m = 1, 2; n = 0, 1) compounds. Previous investigations on the CeMIn5 series indicate that the rich phase diagram of these materials is the result of a subtle balance between the competing Ruderman¿Kittel¿Kasuya¿Yosida interaction, Kondo effect and crystalline electric field effects, influenced by the system¿s dimensionality. Therefore, understanding the evolution of the crystal field in a system whose dimensionality is different from these compounds may allow a deeper understanding of their role in the emergence of interesting phenomena in these systems. The evolution of the physical properties of the Ce2Rh1-xIrxIn8 series and the role of Cd-doping in Ce2MIn8 (M = Rh, Ir) have been previously studied. It has been shown that Ir substitution seems to suppress the antiferromagnetism and induce a coexisting superconducting phase, as well as a disordered spin-glass phase in the Ir-rich compounds. This evolution is accompanied by an enhancement of the Kondo effect and likely changes in the crystal field. On the contrary, Cd-doping in the In site favors antiferromagnetism for M = Rh and suppresses superconductivity for M = Ir, suggesting that the main role of Cd in these systems is the electronic tuning of the ground state properties. In such scenario, evidence arise that the orbital contribution and symmetry properties of the Ce 3+ crystalline electric field ground state wavefunction may play a crucial role on physical properties of these Ce-based families. Then, they have become focus of intense scientific investigation. As such, solving the magnetic structure for the magnetic members of these families can give more insight on the crystal field and ground state of Ce 3+ in these systems, considering the ordered moment's direction and single-ion anisotropy. We synthesized new Ce2Rh1-xIrxIn7.79Cd0.21 single crystals using the metallic-flux method and characterized macroscopically the samples, which follow the expected trend for ordering temperature, the Sommerfeld coefficient and lattice parameters. We also discuss applied pressure effects on Ce2RhIn7.79Cd0.21 and the magnetic structures of the Cd-doped Ce2Rh1-xIrxIn8 (x = 0, 0.5, 1) antiferromagnetic alloys by neutron magnetic diffraction measurements. Regarding the pressure-dependent magnetic structure of Ce2RhIn7.79Cd0.21, for low applied pressures the compound showed no changes in the propagation vector nor in the Néel temperature. Yet, increasing pressure seems to induce spin rotation towards the ab-plane. The changes in these magnetic structures were connected to preliminary studies of the crystal field effects using a mean-field model with tetragonal crystalline electric field and exchange interactions. These studies enabled us to propose crystal field schemes and some general trends over the separation of crystal field levels, shedding light on the origin of the spin rotation under pressure and the disordered state in Ir-rich compounds (AU) | |
| FAPESP's process: | 19/04196-3 - Investigation of crystalline electric field effects in magnetic and superconducting states in the Ce2RhIn8-xCdx compounds |
| Grantee: | Denise Sacramento Christovam |
| Support Opportunities: | Scholarships in Brazil - Master |