Competition between disorder and exchange splitting in superconducting ZrZn_2

We propose a simple picture for the occurrence of superconductivity and the pressure dependence of the superconducting critical temperature, T_{SC}, in ZrZn_2. According to our hypothesis the pairing potential is independent of pressure, but the exchange splitting, E_{xc}, leads to a pressure dependence in the (spin dependent) density of states at the Fermi level, D_\sigma(\epsilon_F). Assuming p-wave pairing T_{SC} is dependent on D_\sigma(\epsilon_F) which ensures that, in the absence of non-magnetic impurities, T_{SC} decreases as pressure is applied until it reaches a minimum in the paramagnetic state. Disorder reduces this minimum to zero, this gives the illusion that the superconductivity disappears at the same pressure as ferromagnetism does.