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Disordered magnets: ground state, excitations, and thermodynamics


Disorder is ubiquitous in solids. In magnets with localized spin moments, typical examples of disorder are missing or extra spins, arising, e.g., from chemical substitution. In this project, we study two classes of disordered magnets: with and without long range magnetic order. For magnets which display a ground state with long range magnetic order, we consider the effects of impurities, generally vacancies, in spin-S frustrated antiferromagnets. We investigate the (singular) behavior of the impurity induced spin texture as a function of an external magnetic field as well as its signatures in several physical observables. For the class of magnets without long range magnetic order, we consider in particular quantum paramagnets with spontaneous or disorder induced dimerization. We propose here the development of a flexible method applicable both to finite disorder and to a temperature interval experimentally relevant. Specifically, our investigation is based on an extension of the bond operator formalism to inhomogeneous magnetic systems. We obtain not only thermodynamic quantities, but also the magnetic excitation spectra, as measured by inelastic neutron scattering, which have been increasingly experimentally accessed. (AU)

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Scientific publications (6)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
JANSSEN, LUKAS; ANDRADE, ERIC C.; VOJTA, MATTHIAS. Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for alpha-RuCl3 and Na2IrO3. Physical Review B, v. 96, n. 6, . (13/00681-8)
ANDRADE, ERIC C.; JAGANNATHAN, ANURADHA; MIRANDA, EDUARDO; VOJTA, MATTHIAS; DOBROSAVLJEVIC, VLADIMIR. Non-Fermi-Liquid Behavior in Metallic Quasicrystals with Local Magnetic Moments. Physical Review Letters, v. 115, n. 3, . (13/00681-8)
SARKAR, R.; KRIZAN, J. W.; BRUECKNER, F.; ANDRADE, E. C.; RACHEL, S.; VOJTA, M.; CAVA, R. J.; KLAUSS, H. -H.. Spin freezing in the disordered pyrochlore magnet NaCaCo2F7: NMR studies and Monte Carlo simulations. Physical Review B, v. 96, n. 23, . (13/00681-8)
CANTARINO, M. R.; AMARAL, R. P.; FREITAS, R. S.; ARAUJO, J. C. R.; LORA-SERRANO, R.; LUETKENS, H.; BAINES, C.; BRAUNINGER, S.; GRINENKO, V; SARKAR, R.; et al. Dynamic magnetism in the disordered hexagonal double perovskite BaTi1/2Mn1/2O3. Physical Review B, v. 99, n. 5, . (13/00681-8, 15/16191-5)
ANDRADE, ERIC C.; HOYOS, JOSE A.; RACHEL, STEPHAN; VOJTA, MATTHIAS. Cluster-Glass Phase in Pyrochlore XY Antiferromagnets with Quenched Disorder. Physical Review Letters, v. 120, n. 9, . (13/00681-8, 15/23849-7, 16/10826-1)
JANSSEN, LUKAS; ANDRADE, ERIC C.; VOJTA, MATTHIAS. Honeycomb-Lattice Heisenberg-Kitaev Model in a Magnetic Field: Spin Canting, Metamagnetism, and Vortex Crystals. Physical Review Letters, v. 117, n. 27, . (13/00681-8)

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