Miniaturized torquemeter for magnetization studies in high-Tc microcrystals

A new integrated torque magnetometer based on piezoresistive cantilevers has been developed. The miniaturized device with dimensions of 150× 100× 4 μm allows the measurement of magnetic moments through the detection of the magnetic torque τ = m× B with a sensitivity of Δτ = 10^-14 Nm. In an applied field of B=1 T magnetic moments as small as 10^-14 Am^2 can be detected, a value three orders of magnitude better than that achieved in commercial SQUID magnetometers. The novel torque magnetometer is particularly suited for angle-dependent magnetization studies in submicrogram high-T_c crystallites. Measurements on Bi_2Sr_2CaCu_2O₈ and HgBa_2Ca_3Cu_4O_10 microcrystals demonstrate the excellence performance of this device. In particular, flux-creep and pinning properties of the flux line lattice can be investigated and quantities such as the effective mass anisotropy ratio γ , the in-plane coherence length ξ_ab and the penetration depth λ_ab are derived very precisely.