Magnetic-Field Induced Slow Relaxation in the Ising-Like Quasi-One-Dimensional Ferromagnet KEr(MoO₄)₂

We present the study of spin dynamics of KEr(MoO₄)₂ in the magnetic field applied along the hard axis c. The temperature dependence of AC susceptibility in zero magnetic field studied at frequencies f=10, 100, and 1000 Hz indicated the absence of relaxation in the temperature range from 2 to 20 K. Application of magnetic field induced a slow magnetic relaxation, which was investigated in detail in the field 0.5 T. The highest intensity of the relaxation process, reflected by the values of imaginary susceptibility was observed at 2 K. With increasing temperature, the relaxation process is weaker and vanishes completely above 3.5 K. Corresponding Cole-Cole diagrams were constructed and analyzed within a single relaxation process which can be associated with a direct relaxation process with a bottleneck effect, τ ≈1/T^b, and b=1.4. The slow relaxation at 2 K intensifies with increasing magnetic field at least up to 1 T