Syntheses,structures,andlow-temperature magnetic properties of anhydrous alums

Abstract

In this thesis, anisotropic triangular systems belonging to the anhydrous alum family are studied. A Mo4+ S = 1 system in the form of BaMo(PO4)2 is first presented. Crystallographic determination is carried out using X-ray and neutron powder diffraction studies. Low-temperature magnetic properties are reported by analyzing magnetic susceptibility, specific heat, low temperature neutron powder diffraction, and neutron spectroscopy data. An effective one dimensional Ising Neél state is predicted from the data. Further presented are a continuation of a series of S = 1/2 Ti3+ systems. Those follow the formula ATi(SO4)2 (A=Rb,Cs) and are studied as a continuation of previously reported KTi(SO4)2 [2]. Powder X-ray diffraction is utilized in crystallographic determination. Magnetic susceptibility and specific heat measurements are carried out, and susceptibility analytical expressions for the spin Hamiltonian are used to fit the data. Excellent agreement between collected and fitted data is observed, and a one-dimensional Heisenberg chain is suggested. A trend of increasing one-dimensionality is noted with increasing ionic radius. Magnetic susceptibility, specific heat, and low-temperature neutron powder diffraction data for NaFe(SO4)2 are reported in the Appendix.