Magnetothermodynamics of the Spin-12Kagomé Antiferromagnet

In this paper, we use a new hybrid method to compute the thermodynamic behavior of the spin- $\frac{1}{2}$ Kagomé antiferromagnet under the influence of a large external magnetic field. We find a $T^2$ low-temperature behavior and a very low sensitivity of the specific heat to a strong external magnetic field. We display clear evidence that this low-temperature magnetothermal effect is associated with the existence of low-lying fluctuating singlets, but also that the whole picture ( $T^2$ behavior of $C_v$ and the thermally activated spin susceptibility) implies contribution of both nonmagnetic and magnetic excitations. Comparison with experiments is made.