Critical Crossover Behavior of Itinerant Weak Antiferromagnets around Quantum Critical Point

Magnetic and thermal critical behaviors of itinerant electron magnets around the quantum critical point (QCP) have recently attracted much interest. On the other hand, crossover phenomena between classical and quantum critical behaviors have not drawn much attention. The purpose of this study is, therefore, clarifies how the predominance of thermal and quantum critical behaviors will change around the QCP based on the spin fluctuation theory. We show that in the region very close to the Neel temperature TN in the paramagnetic phase, the temperature dependence of the inverse of staggered susceptibility obeys the classical (T-TN)2-linear behavior. With increasing temperature T, it changes into the quantum critical (T3/2-TN 3/2)-linear dependence above the crossover temperature T*. Since T* tends to vanish in the quantum critical limit TN 0, the classical critical region disappears and predominant T3/2-linear behavior prevails