Authors: M Fiebig
Publish Date: 2002/03/19
Volume: 74, Issue: 7-8, Pages: 749-758
Abstract
Magnetic secondharmonic generation SHG and threephoton differencefrequency generation DFG are used to investigate the magnetic phase diagrams of MnO3 3 compounds with five and sixfold coordination of the Mn3+ 3d4 ion In the hexagonal manganites the six basic antiferromagnetic structures following from a onedimensional representational analysis of the hexagonal unit cell are clearly distinguished on the basis of their different selection rules for SHG All structures break the geometric frustration of the unit cell by triangular antiferromagnetic ordering of the Mn spins The stability and the mutual interactions of inplane and interplane exchange and the inplane anisotropy are investigated The three quantities act as almost decoupled degrees of freedom which leads to independent inplane and interplane reorientations of the Mn spin lattice DFG was observed in the orthorhombic manganites Pr1xCaxMnO3 and Nd1xSrxMnO3 The DFG reflects the fourfold anisotropy of the quasicubic crystal and the independent tensor elements for DFG are determined quantitatively A metal–insulator transition with a twoorderparameter coupling to antiferromagnetism and charge ordering leads to additional differencefrequency contributions which allow us to observe the formation of ∼100 μm magnetic domains The variety of results gained from the two vastly different groups of manganite compounds with spectral and spatial resolution used as additional degrees of freedom demonstrates the versatility of nonlinear magnetooptical experiments for the investigation of magnetic structures and symmetries
Keywords: