Superconducting Quantum Interference Device – SQUID

General Description

SQUID offers the chance to measure the absolut value of magnetic fields in units of the magnetic flux quantum. The device is capable of applying magnetic fields ranging from -6 T to +6 T and covers a temperature range from (5-400)K. Besides hysteresis loops, i.e. the dependence of the magnetization on the applied magnetic field M(H), the temperature dependence M(T) can be measured as well. Examples are shown below. Example 1 is the temperature dependence of the magnetization for a FeTb alloy. The Fe atoms are ferromagnetically coupled, just the same as the Tb atoms. However, the two sublattices Fe and Tb are antiferromagnetically coupled. Since these two sublattices exhibit different temperature dependencies a compensation point has to occur in the M(T) curve, as shown below. Example 2 shows the temperature dependence of the diluted ferromagnetic semiconductor (Ga,Mn)As.