Pauli Paramagnetism in a Fermi Glass

A broad Lorentzian ESR line in H-doped Ca${\mathrm{V}}_2$ ${\mathrm{O}}_6$crystals has been observed and assigned to itinerant electrons in $d_{x^2-y^2}$ orbitals. The spin susceptibility and the ESR linewidth vary weakly between 20 and 300 K, whereas the conductivity varies strongly, consistent with Mott's $\exp -{\left(\frac{T_0}{T}\right)}^{\frac{1}{4}}$ variable-range hopping law for random systems. Our observations demonstrate the existence of Fermi statistics in this system of protons and $d$ electrons which may be more clustered than purely random.