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Magnetic susceptibilities have been measured in the temperature region 1.7–60°K both parallel and perpendicular to the chemical chain on single crystals of Cu(pyrazine)(NO3)2. It has been shown that there is qualitative disagreement between experiment and theory if the appropriate equations derived for the Ising model in one dimension are applied. On the other hand, excellent agreement exists for the Heisenberg model with J/k = −5.3°K down to the lowest temperature achieved, along with closer agreement between the g values determined in this experiment and those obtained by EPR. A comparison is also made between the exchange pathway in Cu(NO3)2 · 2.5H2O and the probable pathway in Cu(pyrazine)(NO3)2.

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Magnetic susceptibility measurements on powdered samples of bis(benzylammonium) tetrachlorocuprate (II), bis(phenethylammonium) tetrachlorocuprate(II), bis(3-phenyl-1-propylammonium) tetrachlorocuprate(II), and bis(benzylammonium) tetrabromocuprate(II) have shown that these four substances order ferromagnetically with Curie temperatures of 8.0±0.5, 9.0±0.2, 7.0±0.5, and 12.3±1.0 K, respectively. Fits of a series expansion for a two-dimensional lattice to the magnetic susceptibility data obtained from powdered samples in the paramagnetic region yielded exchange constants J for the chloride compounds in the range 16.7–18.8 K, and a value of 25.3 K for the bromide compound. For these fits the <g≳ value of 2.14±0.01 determined from EPR measurements was used. Magnetic susceptibility measurements made at 10 Oe on a single crystal of bis(phenethylammonium) CuCl4 at temperatures just below Tc revealed ratios of susceptibilities of 30:7:1 along the c, a, and b axes, respectively, where the b axis is perpendicular to the thin tabular plates. Magnetization measurements on a single crystal sample of this compound showed that the easy axis, the c axis, and the next-preferred axis, the a axis, were saturated above 60 and 200 Oe, respectively, while magnetic fields greater than 1800 Oe were required for saturation along the b axis. Magnetization measurements on a single crystal of bis(benzylammonium) tetrabromocuprate(II) did not reveal any anisotropy within the plane of the plate, where the saturation field was 50 Oe at 4.2 K, while a field of 1800 Oe was required for saturation along the direction perpendicular to the plate. Anisotropy fields derived from the magnetic susceptibility and magnetization data obtained from measurements on single crystals of bis(benzylammonium) tetrachlorocuprate(II) and bis(phenethylammonium) tetrachlorocuptrate(II) cannot be explained by the calculated exchange and dipolar fields, and it is suggested that an additional mechanism contributes to the anisotropy.