The Triangular Planar TP Lattice

While the TP lattice is realised in many inorganic materials, the transition metal di- and trihalides such as CrX3 or NiXy, where X is a Cl, Br or I, come to mind, for most of these the nn, intraplanar exchange is F and frustration does not play a role. In part this is due to the predominance of intraplanar 90° M-X-M superexchange which is often F. The salts,VBr2 and VCL, do appear to have intraplanar AF 

AgCr02 and CuCr02 also exhibit complex magnetic order with wave vectors k = (0.3270.3270) and k= (1/3 1/3 ), respectively, i.e. modulated 120° structures. 

In addition the magnetic Bragg peaks exceed the resolution width, indicating that LRO is not truly established in three dimensions. 

In Table 2.1 we collect some relevant data for selected TP systems. 

M+ and order into layers normal to the body diagonal 111 of the NaCl cubic cell (FmSm — flSm) 

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