Magnetic resonance of the RbMnBr$_3$ antiferromagnet under pressure

The antiferromagnetic resonance spectrum was experimentally studied for a noncollinear RbMnBr$_3$ antiferromagnet under a mechanical pressure applied to the sample in various directions. It is shown that the incommensurate magnetic phase existing in the initial system in the presence of regular crystallographic distortions is sensitive to the pressure applied along one of the sample axes. The critical transition field to the commensurate phase decreased under pressure. It was also found that the pressure influences the uniaxial anisotropy appearing in the crystal basal plane in the presence of orthorhombic distortions. These effects were analyzed with allowance for the domain structure of the sample.