Frustrated Magnet Mn3Al2Ge3O12 Garnet: Crystal Growth by the Optical Floating Zone Method

Abstract

Mn3Al2Ge3O12 is a member of the garnet family of compounds, A3B2(CO4)3, whose magnetic properties are affected by a high degree of geometrical frustration. The magnetic frustration is at the origin of the intriguing magnetic properties that these materials exhibit, such as a long range hidden order derived from multipoles formed from 10-spin loops in the gadolinium gallium garnet, Gd3Ga5O12. Mn3Al2Ge3O12 garnet is isostructural to the thoroughly investigated Gd garnets, Gd3Ga5O12 and Gd3Al5O12. Moreover, in Mn3Al2Ge3O12, the Heisenberg-like Mn2+ magnetic ions (L= 0) are also arranged in corner sharing triangles that form a hyperkagomé structure. The identical crystallographic structures and similar Heisenberg-like behaviour of the magnetic ions make manganese aluminium germanium garnet the closest compound to the gadolinium garnets in its magnetic properties. Here, we report, for the first time, the growth of a large, high quality single crystal of the Mn3Al2Ge3O12 garnet by the floating zone method. X-ray diffraction techniques were used to characterise and confirm the high crystalline quality of the Mn3Al2Ge3O12 crystal boule. Temperature-dependent magnetic susceptibility measurements reveal an antiferromagnetic ordering of the Mn2+ ions below TN= 6.5 K. The high quality of the single crystal obtained makes it ideal for detailed investigations of the magnetic properties of the system, especially using neutron scattering techniques.