De Haas-van Alphen oscillations in a single crystal of ZrZn2

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Abstract
Two de Haas-van Alphen frequencies, 14.5+or-0.2 and 16.2+or-0.2 MG, have been observed in a single crystal of ZrZn2. The magnetic field was parallel to the (1,1,5) direction. All the other orientations tested yielded the same frequencies, within the limits set by uncertainties in the demagnetising factor and the number of oscillations detected. These results restrict possible interpretation in terms of available band calculations, to a Gamma -centred spherical sheet of Fermi surface, split in two for the spin-up and spin-down sub-bands. The difference in cross-sectional area between these two surfaces corresponds to the observed frequency separation of 1.7 MG. This separation, combined with the calculated band velocity, gives an exchange splitting of 4.5 mRyd. The two frequencies had the same effective mass m*/mo=0.90+or-0.05. Comparison with the calculated band mass gives a phonon and magnon mass enhancement parameter of lambda =1.7.