Volume dependence of the Fermi surface and of the spin-density-wave Q vector in antiferromagnetic chromium

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Abstract
The volume dependence of extremal cross-sectional areas of the Fermi surface of antiferromagnetic chromium is obtained from de Haas-van Alphen experiments under pressures up to 4 kbar. The experimental data analysed in terms of a nesting-model lead to d ln(Qa)/dp=-0.49*10-6 bar-1 for the pressure dependence of the spin-density-wave Q vector. This value which is in good agreement with results obtained from neutron diffraction is approximately one order of magnitude larger than the calculated pressure derivative of the geometrical nesting vector. It is also much larger than the value d ln(Qa)/dp approximately=0.01*10-6 bar-1 obtained from oscillatory magnetostriction and de Haas-van Alphen torque measurements. This discrepancy is believed to be due to a pinning of the incommensurate spin-density-wave to the lattice. Experimental evidence for such a pinning mechanism is briefly discussed.