Manifestation of Memory and Butterfly in the Photon Echo on Erbium Ions in LuLiF4 and YLiF4.

The memory effect in the form of hysteresis has been detected in the measured dependence of the intensity of the photon echo in YLiF4 and LuLiF4 samples with Er3+ impurity ions on the orientation, strength, and variation direction of the magnetic field. The prehistory of the location of a sample in the magnetic field with a certain direction and strength is written and stored for no less than 6 h at a temperature of 2 K. The effect crucially depends on the orientation of the optical axis of the sample with respect to the external magnetic field. [ABSTRACT FROM AUTHOR]