TI₂Ba₂CaCu₂O_x Bicrystal Junction DC-SQUID Magnetometers Operating in Unshielded Environment

We fabricated direct-current superconducting quantum interference device magnetometers with single layer epi-taxial Tl₂Ba₂CaCu₂O_x films on 36.8^o SrTiO₃ bicrystal substrates. The white Aux noise and the field-flux transformation coefficient of the devices are 1.5 x 10^-5Φ₀/√Hz and 40 nT/Φ₀, respectively. The magnetometers can work in unshielded environment.