Abstract
A magnetic field applied to a three-dimensional antiferromagnetic metal can destroy the long-range order and thereby induce a quantum critical point. Such field-induced quantum critical behavior has been the focus of many recent experiments. We theoretically investigate the quantum critical behavior of clean antiferromagnetic metals subject to a static, spatially uniform, external magnetic field. The external field not only suppresses (or induces in some systems) antiferromagnetism, but also influences the dynamics of the order parameter by inducing spin precession. This leads to an exactly marginal correction to spin-fluctuation theory. We investigate how the interplay of precession and damping determines the specific heat, magnetization, magnetocaloric effect, susceptibility, and scattering rates. We point out that precession can change the sign of the leading correction to the specific-heat coefficient and can induce a characteristic maximum in for certain parameters. We argue that the susceptibility is the thermodynamic quantity that shows the most significant change upon approaching the quantum critical point, and which gives experimental access to the (dangerously irrelevant) spin-spin interactions.
1 More- Received 13 December 2004
DOI:https://doi.org/10.1103/PhysRevB.71.184429
©2005 American Physical Society