Magnetic transitions in the insulator nickel squarate dihydrate, NiC4O4·2H2O

Abstract
The real and imaginary initial susceptibilities of two samples of nickel squarate dihydrate, NiC4O4·2H2O have been measured in the range 1.2–4°K. Both samples exhibited deviations from Curie‐Weiss behavior and magnetic losses characteristic of ferromagnetic ordering. Magnetic transitions were found in both samples in the neighborhood of 1.6 and 1.9°K, the higher temperature transition occuring at 1.8°K in a sample grown from an alcohol‐water solution, and at 2.1°K in a sample grown from a pure water solution. The difference in magnetic behavior of the two samples is thought to be related to the type of solvent molecule clathrated by the open NiC4O4·2H2O structure.