Pressure-Induced Transition from an Antiferromagnet to a Ferrimagnet for Mn^II(TCNE)[C₄(CN)₈]_1/2 (TCNE = Tetracyanoethylene)

Abstract

Mn(II)(TCNE)[C(4)(CN)(8)](1/2) (TCNE = tetracyanoethylene) exhibits a reversible pressure-induced piezomagnetic transition from a low magnetization antiferromagnetic state to a high magnetization ferrimagnetic state above 0.50 ± 0.15 kbar. In the ferrimagnetic state, the critical temperature, T(c), increases with increasing hydrostatic pressure and is ~97 K at 12.6 kbar, the magnetization increases by 3 orders of magnitude (1000-fold), and the material becomes a hard magnet with a significant remnant magnetization.

Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

“…The J i values increase with increasing pressure on account of closer intermolecular contacts enforcing stronger exchange coupling between adjacent Re IV centres at each increased pressure. Pressure-induced enhancement of T c has been previously reported through SQUID magnetometry in 3D ferro- and ferrimagnets, and in weak ferromagnets containing transition metal ions353637383940414243, although in each case no structural information was forthcoming, preventing unequivocal explanation of the observed magnetic changes. The present study represents the first combined high-pressure single-crystal X-ray crystallography—high-pressure magnetism study of an ordered 5d molecule-based material.…”

Radicals in metal–organic frameworks

“…TCNEc À has received signicant attention as a component of frameworks which are of interest for their intriguing magnetic properties which include high ordering temperatures (T C as high as 400 K) and high coercive elds (up to 27 000 Oe). 50 Two major families of 3D networks containing the radical anion ligand have been intensively investigated in recent years by Miller and co-workers, namely M II (TCNE) [C 4 (CN) 8 ] 1/2 $zCH 2 Cl 2 (M ¼ Mn, Fe) 51,52 and Mn II (TCNE) 3/2 (I 3 ) 1/ 2 $zTHF. 53 In the former case, corrugated layers of M II bonded to four m 4 -[TCNEc À ] (S ¼ 1/2) are bridged by the diamagnetic m 4 -[C 4 (CN) 8 ] 2À dimer (S ¼ 0) to yield a structure commonly formulated as M II [m 4 -[TCNE]c À (m 4 -[C 4 (CN) 8 ] 2À ) 1/2 .…”

A collapse of ferromagnetism in an organic based magnet under pressure

“…Encouragingly, the data lie almost on a straight line, with a slope of -2.06(7) K/kbar although to create a more reliable phase diagram, more work is needed. The pressure dependence of T C within other metal-organic systems can vary hugely [23,24], however Ni(TCNQ) 2 is a fairly simple system, not containing any additional ligands, and to our knowledge this is the first report showing this type of behaviour in these M(TCNQ) 2 salts. Within this low temperature region, there are only two scenarios that, either the sample is ferromagnetic, ferrimagnetic or paramagnetic, however with more work hopefully this can be expanded to see if there are any other more exotic forms of magnetism present.…”