Magnetization measurements under pressure reveal that the external hydrostatic pressure significantly increases in the ferrimagnetic transition temperature, T, for AMn[Mn(CN)] (A = K, Rb, Cs). In the case of monoclinic A = K and Rb, dT/dp values are 21.2 and 14.6 K GPa, respectively, and T increases by 53 and 39%, respectively, from ambient pressure to 1.0 GPa. The cubic A = Cs compound also shows a monotonous increase with an initial rate of 4.22 K GPa and about 11.4 K GPa above 0.6 GPa, and an overall T increase by 26% at 1.0 GPa. The increase in T is attributed to deformation of the structure such that the Mn-N≡C angle decreases with increasing pressure. The smaller the alkali cation, the greater the decrease in the Mn-N≡C angle induced by pressure and the larger the increase of dT/dp. This is in accordance with the ambient-pressure structures for AMn[Mn(CN)] (A = K, Rb, Cs), which have decreasing Mn-N≡C angles that correlate to the observed increasing Ts as K > Rb > Cs. The large increase in T for the A = K compound is the highest class among several cyano-bridged metal complexes. The tuning of the transition temperature by such a weak pressure may lead to additional applications such as switching devices.

The magnetic behaviors of the metamagnetic and ferromagnetic polymorphs of [Fe(III)Cp(2)*](•+)[TCNQ](•-) (Cp* = pentamethylcyclopentadienide; TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) were studied as a function of hydrostatic pressure. Both polymorphs exhibit a reversible enhancement of magnetic properties with increasing pressure. The T(c) for the ferromagnetic polymorph increased by 70% from 2.95 to 5.01 K at 10.3 kbar at a rate of 0.21 K/kbar, which is similar to the 0.22 K/kbar reported for [FeCp(2)*](+)[TCNE](-). The coercive field and remnant magnetization exhibit exponential-like growth upon application of external pressure, increasing from zero at ambient pressure to 550 Oe and 8880 emu·Oe/mol at 10.3 kbar, respectively. The T(c) for the metamagnetic polymorph was determined to be 2.10 K from the maximum in the Fisher specific heat data, that is, d(χT)/dT, and it increases by 38% to 2.90 K at 2.9 kbar at a rate of 0.28 K/kbar, before vanishing, in accord with a transition to a paramagnetic state. The metamagnetic critical field, H(c), determined from dM/dH increases linearly from 1300 Oe at ambient pressure to 1800 Oe at 2.9 kbar, but is not evident at and above 3.9 kbar, also in accord with a transition to a paramagnetic state.

To identify the genesis of the differing magnetic behaviors for the ferro- (FO) and metamagnetic (MM) polymorphs of [FeCp*2][TCNQ] (Cp* = pentamethylcyclopentadienide; TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) the low temperature (18 ±...

Mean field expressions based on the simple Heisenberg model were derived to correlate the intra- and interlayer exchange couplings to the critical temperatures, T c, for three metallocyanide-based magnets with extended 2- and 3-D structure types. These expressions were used to estimate the exchange coupling, J, for 2-D ferrimagnetic [NEt4]2MnII 3(CN)8, 3-D antiferromagnetic [NEt4]MnII 3(CN)7, and 3-D antiferromagnetic interpenetrating 3-D MnII(CN)2. The type and magnitude of the exchange coupling are in accord with the previously reported magnetic data.

The magnetic properties of [Fe(III)Cp*2]˙(+)[HCBD]˙(-) (Cp* = pentamethylcyclopentadienide; HCBD = hexacyanobutadienide, C4(CN)6) and [Fe(III)Cp*2]˙(+)[DDQ]˙(-) (DDQ = 2,3-dichloro-5,6-dicyanoquinonide) were measured at ambient and applied hydrostatic pressures up to 11.4 and 9.2 kbar, respectively. At ambient pressure [FeCp*2][HCBD] exhibits spin glass-like behavior with a freezing temperature, Tf, of 2.93 K from the peak in χ'(T) at 10 Hz, but magnetic ordering is not evident due to the lack of a remnant magnetization, bifurcation temperature, and hysteresis. Above 3.1 kbar, [FeCp*2][HCBD] magnetically orders as a metamagnet with an antiferromagnetic ground state with an ordering temperature, Tc, of 2.46 K determined from the Fisher specific heat, which increases linearly to 4.80 K at 11.4 kbar at a rate of 0.28 K kbar(-1). Upon application of pressure metamagnetic-like behavior with hysteresis indicative of a weak ferromagnet (canted antiferromagnet) was observed at and above 3.1 kbar, with a coercive field, Hcr, of 65 Oe, which increases exponentially to 795 Oe at 11.4 kbar. [FeCp*2]˙(+)[DDQ]˙(-) did not magnetically order above 2 K, and magnetic order was not observed up to 9.2 kbar. The pressure dependencies are reversible.