Low-symmetric quantum magnets as a step to terahertz invisibility

Quantum spin systems with low symmetries of the magnetic properties are studied. It is shown that the low symmetry yields special effects of their magnetic characteristics. Magnetic moments induced by the external magnetic field can be nonparallel to the direction of the field. Also, components of the magnetic susceptibility of such systems can be negative in a large range of the field and temperature values, i.e., they manifest diamagnetic behavior. The origin of the effect is totally quantum. Such a behavior is generic for quantum paramagnets, low-dimensional quantum spin systems, and for quantum spin systems with geometrical frustration of spin-spin couplings. The effect can be important for applications of such quantum systems, e.g., in the creation of metamaterials or in quantum computing.