A theory of uniform spin susceptibility around the antiferromagnetic quantum critical point

The uniform spin susceptibility chi around the quantum critical point is discussed on the basis of the mode-mode coupling theory of the antiferromagnetic (AF) spin fluctuations. The temperature dependence of chi around the quantum critical point reflects the magnetic-field dependence of the free energy due to that of the spin fluctuations. The results are chi proportional to 1 - beta(2)t(1/4) for the conventional class of AF fluctuations with the dynamical exponent z = 2, and chi proportional to 1 - beta(3)t(1/3) for a new class of AF fluctuations with z = 3, where t is the reduced temperature and beta(2) and beta(3) are numerical constants. For Ce7Ni3, the behavior of chi around the quantum critical point is possibly explaned by this theory with the conventional class of AF fluctuations with 2 = 2. The latter type of AF fluctuations with 2 = 3 is possible when the system contains even number of magnetic ions in the unit cell such as CeCu6-xAux (x = 0.1), because the AF ordering vector can coincide with one of the reciprocal lattice vectors.