Magnetic Ordering (T_c = 90 K) Observed for Layered [Fe^II(TCNE^•-)(NCMe)₂]⁺[Fe^IIICl₄]^- (TCNE = Tetracyanoethylene)

Abstract

[Fe(TCNE)(NCMe)2][FeCl4] is isolated from the reaction of TCNE and FeCl2(NCMe)2 and orders as a ferrimagnet below 90 K and is the initial member of a new class of magnets. It is the first metal-TCNE magnet with direct bonding between metal ion and [TCNE]*- whose structure has been determined, and it possesses a novel planar mu4-[TCNE]*- spin coupling unit bonded to four FeII's, with an axial pair of MeCNs. The [FeIIICl4]- anion occupies sites between the [FeII(TCNE*-)(NCMe)2]+ layers. [Fe(TCNE)(NCMe)2][FeCl4] has a coercive field of 1730 Oe and a remnant magnetization of 7500 emuK/mol at 50 K.

Magnetic Bistability and Nucleation of Magnetic Bubbles in a Layered 2D Organic-Based Magnet[Fe(TCNE)(NCMe)2][

“…In this Letter, we report unique properties of magnetic bistability of the 2D layered system ½FeðTCNEÞ-ðNCMeÞ 2 ½FeCl 4 (TCNE ¼ tetracyanoethylene) [14]. The dc magnetization displays anomalous irreversibility between zero-field-cooled (ZFC) and field-cooled (FC) states, which we propose to originate from magnetization reversal of single 2D layers through the nucleation and growth of ''bubble domains.''…”

“…The ZFC magnetization is not only strongly suppressed below the irreversible temperature, T ir , but it is also nearly negligible over a wide temperature range below T c at low field. The ac susceptibility also exhibits the slowing down of spin dynamics as temperature (T) decreases through T c , which was attributed to spin glasslike behavior [14]. The strong irreversibility may be attributed PRL 101, 197206 (2008) …”

“…Notable examples are spin-crossover complexes, which exhibit thermal transition between high-spin and low-spin states [4], high-spin complexes, which demonstrate macroscopic quantum tunneling of magnetization [5,6] and mixed ferro-ferrimagnetic Prussian blue analogs, which display multiple compensation temperatures [7]. In addition, their magnetic bistabilities often can be controlled by the optical excitation [8][9][10][11][12][13].In this Letter, we report unique properties of magnetic bistability of the 2D layered system ½FeðTCNEÞ-ðNCMeÞ 2 ½FeCl 4 (TCNE ¼ tetracyanoethylene) [14]. The dc magnetization displays anomalous irreversibility between zero-field-cooled (ZFC) and field-cooled (FC) states, which we propose to originate from magnetization reversal of single 2D layers through the nucleation and growth of ''bubble domains.''…”

“…The absence of bridging ligands between the layers suggests only dipolar coupling exists between the layers. In each layer, the magnetic coupling between spin in ½TCNE ÁÀ (S ¼ 1=2) and spins in Fe II (S ¼ 2) is suggested to be antiferromagnetic resulting in ferrimagnetic order [14] similar to other metal-TCNE magnets [15][16][17][18]. Thus, each individual layer is considered as an ideal 2D ferrimagnetic Ising system.…”

“…There are no covalent bonds between layers [14]. Additional paramagnetic ½FeCl 4 À anions occupy sites between the layers of ½FeðTCNEÞ-ðNCMeÞ 2 þ but do not contribute to the magnetic ordering [14]. The absence of bridging ligands between the layers suggests only dipolar coupling exists between the layers.…”