We discuss briefly various measuring techniques and review the basic concepts of a new micro-SQUID technique which allows one to study single nanometer-sized magnetic particles at low temperature. In the case of sufficiently small particles, the magnetization reversal occurs by uniform rotation and the measurement of the angular dependence of the magnetization reversal yields the effective magnetic anisotropy. The influence of the temperature on the magnetization reversal is discussed.

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... ties of switching, switching field distributions, and telegraph noise measurements are proposed to check the predictions of the Néel-Brown theory describing thermal activated magnetization reversal. At very low temperature, we will see how quantum effects can be revealed.