E. Svanidze, Jiakui K. Wang, T. Besara, L. Liu, Q. Huang, T. Siegrist, B. Frandsen, J.W. Lynn, Andriy H. Nevidomskyy, Monika Barbara Gamża, M.C. Aronson, Y.J. Uemura, E. Morosan, "An itinerant antiferromagnetic metal without magnetic constituents" Nat. Commun. 6, 7701 (2015)
E. Svanidze, L. Liu, B. Frandsen, B. D. White, T. Besara, T. Goko, T. Medina, T. J. S. Munsie, G. M. Luke, D. Zheng, C. Q. Jin, T. Siegrist, M. B. Maple, Y. J. Uemura, and E. Morosan, "Non-Fermi Liquid Behavior Close to a Quantum Critical Point in a Ferromagnetic State without Local Moments" Phys. Rev. X 5, 011026 (2015)
Eteri Svanidze, Emilia Morosan, "Cluster-glass behavior induced by local moment doping in the itinerant feromagnet Sc3.1In" Phys. Rev. B 88, 064412 (2013)
Itinerant Moment Magnetism
Magnetism can arise through two substantially different mechanisms, resulting in local and itinerant moments, which still rely on distinct theoretical formulations. Most real systems lie somewhere between the local-itinerant extremes, and while numerous local or intermediate moment systems have been synthesized and characterized, comparatively fewer itinerant moment systems have been discovered. Our group is interested in uncovering novel itinerant moment systems to better inform the theories behind magnetism, and to understand how local and itinerant scenarios come together.
TiAu: tuning the first itinerant antiferromagnet to a QCP
We discovered the orthorhombic TiAu to order antiferromagnetically below TN = 36 K with a paramagnetic moment close to 0.8 µB, nearly an order of magnitude smaller than the ordered moment. The magnetic order can be suppressed to uncover quantum critical behavior via Scandium doping, where we observed non-Fermi liquid behavior in the resistivity and specific heat near the critical concentration of xc = 0.13. Meanwhile, pressure studies on pure TiAu revealed a slight enhancement of the magnetic order up to 6 GPa, after which TN decreases monotonically down to approximately 22 K at a pressure of 27 GPa. Meticulous resistivity analysis showed a suppression of the T3 dependence in the ordered state that marks the antiferromagnetic transition, moving towards Fermi liquid behavior that is sustained even in the paramagnetic state.
Scandium doping in TiAu induces a quantum critical point in Ti(1-x)Sc(x)Au around a critical composition xc=0.13, accompanied by non-Fermi liquid behavior.
ZrZn2 Analogues: Exploring Itinerant Magnetism through Atomic Substitutions
ZrZn2 is an itinerant ferromagnet—one of only two ferromagnets without local magnetic moments. Studies have shown that the weak ferromagnetism in this compound is very fragile: partial substitution of Zn2 for CuAl, which is both isoelectronic and of similar size to Zn2, destroys the itinerant magnetic behavior. Further study into this puzzling behavior may reveal the mechanism by which magnetism manifests in purely itinerant systems. With the aid of bandstructure calculations as a predictive tool, synthesis of analogous structures may provide suitable candidates for study and establish a firm experimental basis for the development of a complete theory of itinerant magnetism.
Sc3.1In: NFL behavior close to a QCP
Quantum phase transitions occur at absolute zero temperature and, in contrast to classical phase transitions, are driven by quantum rather than thermal fluctuations. Such transitions have been studied in a large number of magnetic compounds. Only a small number of itinerant moment systems have been known to exhibit quantum critical points (QCPs), with the majority of quantum critical systems being those with local-moment magnetism.
Sc3In is one of only two known itinerant ferromagnets without local moments. We recently showed that the magnetic state is described by non-mean-field crtical exponents, while doping with Lu drove the system to a quantum critical point (QCP) through a non-Fermi liquid (NFL) state.