E.P.R. study of Mn2+ in lithium potassium tartrate (LPT) and its isomorphism with lithium ammonium tartrate (LAT)

An E.P.R. study of Mn²⁺ in single crystals of LiKC₄H₄O₆. H₂O (LPT) was carried out from ～300 K to 77 K and four magnetically differently oriented but symmetry related triclinic complexes of Mn²⁺ were observed. Spin hamiltonian parameters were obtained at ～ 300 K. The E.P.R. results suggest that LPT is not only isomorphous but also isostructural to LiNH₄C₄H₄O₆ . H₂O (LAT). In LPT no structural phase transition could be detected in the temperature range 300 K to 77 K. The observed small magnitude of the low symmetry effect is attributed to the small contribution of fourth order crystal field terms relative to that of the second order crystal field terms, to the zero-field splittings of the ⁶ S ground state of Mn²⁺. A temperature dependent anomalous behaviour is observed in the low field region of the E.P.R. spectrum for B//010] and its neighbourhood.