Vivien Zapf
Los Alamos National Laboratory
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Publication
Featured researches published by Vivien Zapf.
Journal of the American Chemical Society | 2016
L. Claudia Gómez-Aguirre; B. Pato-Doldán; J. Mira; S. Castro-García; M. A. Señarís-Rodríguez; M. Sánchez-Andújar; John Singleton; Vivien Zapf
We present the first example of magnetic ordering-induced multiferroic behavior in a metal-organic framework magnet. This compound is [CH3NH3][Co(HCOO)3] with a perovskite-like structure. The A-site [CH3NH3](+) cation strongly distorts the framework, allowing anisotropic magnetic and electric behavior and coupling between them to occur. This material is a spin canted antiferromagnet below 15.9 K with a weak ferromagnetic component attributable to Dzyaloshinskii-Moriya (DM) interactions and experiences a discontinuous hysteretic magnetic-field-induced switching along [010] and a more continuous hysteresis along [101]. Coupling between the magnetic and electric order is resolved when the field is applied along this [101]: a spin rearrangement occurs at a critical magnetic field in the ac plane that induces a change in the electric polarization along [101] and [10-1]. The electric polarization exhibits an unusual memory effect, as it remembers the direction of the previous two magnetic-field pulses applied. The data are consistent with an inverse-DM mechanism for multiferroic behavior.
Physical Review Letters | 2006
Vivien Zapf; Zocco D; Hansen Br; M. Jaime; N. Harrison; Cristian D. Batista; M. Kenzelmann; Ch. Niedermayer; A. Lacerda; A. Paduan-Filho
It has recently been suggested that the organic compound NiCl2-4SC(NH2)2 (DTN) undergoes field-induced Bose-Einstein condensation (BEC) of the Ni spin degrees of freedom. The Ni S = 1 spins exhibit three-dimensional XY antiferromagnetism above a critical field H(c1) approximately 2 T. The spin fluid can be described as a gas of hard-core bosons where the field-induced antiferromagnetic transition corresponds to Bose-Einstein condensation. We have determined the spin Hamiltonian of DTN using inelastic neutron diffraction measurements, and we have studied the high-field phase diagram by means of specific heat and magnetocaloric effect measurements. Our results show that the field-temperature phase boundary approaches a power-law H - H(c1) proportional variant T(alpha)(c) near the quantum critical point, with an exponent that is consistent with the 3D BEC universal value of alpha = 1.5.
Physical Review B | 2011
S. Yáñez-Vilar; E. D. Mun; Vivien Zapf; B. G. Ueland; J. S. Gardner; J. D. Thompson; John Singleton; M. Sánchez-Andújar; J. Mira; N. Biskup; M. A. Señarís-Rodríguez; C. D. Batista
We present Lu
Physical Review B | 2015
R. D. Johnson; S. C. Williams; Amir A. Haghighirad; John Singleton; Vivien Zapf; Pascal Manuel; I. I. Mazin; Ying Li; Harald O. Jeschke; Roser Valenti; R. Coldea
{}_{2}
Physical Review Letters | 2008
Christian Rüegg; Klaus Kiefer; B. Thielemann; D. F. McMorrow; Vivien Zapf; B. Normand; Mikhail Zvonarev; Pierre Bouillot; Corinna Kollath; Thierry Giamarchi; Sylvain Capponi; Didier Poilblanc; Daniel Biner; Karl J. Kramer
MnCoO
Physical Review Letters | 2007
S. A. Zvyagin; J. Wosnitza; C. D. Batista; M. Tsukamoto; Naoki Kawashima; J. Krzystek; Vivien Zapf; M. Jaime; N. F. Oliveira; A. Paduan-Filho
{}_{6}
Journal of Applied Physics | 2007
Adolfo Franco Júnior; Vivien Zapf; Paul Egan
, a multiferroic member of the double perovskites that we have investigated using x-ray and neutron diffraction, specific heat, magnetization, electric polarization, and dielectric constant measurements. This material possesses a net electric polarization strongly coupled to a net magnetization below 35 K, despite the antiferromagnetic ordering of the
Nature Communications | 2014
Yoon Seok Oh; Sergey Artyukhin; Junjie Yang; Vivien Zapf; Jae Wook Kim; David Vanderbilt; Sang-Wook Cheong
S=3/2
Journal of Applied Physics | 2012
A. Franco; F. C. e Silva; Vivien Zapf
Mn
Physical Review B | 2009
B. Thielemann; Christian Rüegg; Klaus Kiefer; Henrik M. Rønnow; B. Normand; Pierre Bouillot; Corinna Kollath; Edmond Orignac; R. Citro; Thierry Giamarchi; Andreas M. Läuchli; Daniel Biner; Karl Krämer; F. Wolff-Fabris; Vivien Zapf; M. Jaime; Jochen Stahn; N. B. Christensen; B. Grenier; D. F. McMorrow; J. Mesot
{}^{4+}