Pressure‐Induced Conversion of a Paramagnetic FeCo Complex into a Molecular Magnetic Switch with Tuneable Hysteresis

Abstract

A key challenge in the design of magnetic molecular switches is to obtain bistability at room temperature. Here, we show that application of moderate pressure makes it possible to convert a paramagnetic FeIII2CoII2 square complex into a molecular switch exhibiting a full dia‐ to paramagnetic transition: FeIICoIII ⇔ FeIIICoII. Moreover, the complex follows a rare behavior: the higher the pressure, the broader the magnetic hysteresis. Thus, the application of an adequate pressure allows inducing a magnetic bistability at room temperature with predictable hysteresis width. The structural studies at different pressures suggest that the pressure‐enhanced bistability is due to the strengthening of intermolecular interactions upon pressure increase. An original microscopic Ising‐like model including pressure effects is developed to simulate this unprecedented behavior. Overall, this study shows that FeCo complexes could be very sensitive piezo switches with potential use as sensors.

Observation of Protonation-Induced Spin State Switching in a Cyanido-Bridged {Fe2Co2} Molecular Square

“…On the basis of recent results, we decided to probe the possible occurrence of a pressure-induced transition . Actually, the application of hydrostatic pressure is expected to stabilize the diamagnetic state, whose volume is less than that of the paramagnetic state, because of the shorter Co–N bond length in the Co­(III) LS state (the measurement of the magnetization is limited to the low-temperature range, as above 150 K the magnetization becomes weak and the uncertainties are high).…”

“…On the basis of recent results, we decided to probe the possible occurrence of a pressure-induced transition. 49 Actually, the application of hydrostatic pressure is expected to stabilize the diamagnetic state, whose volume is less than that of the paramagnetic state, because of the shorter Co−N bond length in the Co(III) LS state (the measurement of the magnetization is limited to the low-temperature range, as above 150 K the magnetization becomes weak and the uncertainties are high). Here, the application of hydrostatic pressures of 0.11, 0.50, and 1.05 GPa significantly reduces the χ M T value in the low-temperature range (Figure 5) and leads to a slight shift of the χ M T maximum toward higher temperatures.…”

Elastic Origin of the Unsymmetrical Thermal Hysteresis in Spin Crossover Materials: Evidence of Symmetry Breaking

“…The spin-crossover transition (SCO) is a phenomenon that occurs in transition metal coordination compounds based on Fe (II), Fe (III), Mn (II), Mn (III), Co (III), Cr (II) [1][2][3][4][5] which change their spin state due to external stimuli such as a variation of temperature [6][7][8], pressure [9][10][11], light irradiation [12][13][14][15][16], electrical or magnetic fields [17,18] etc. In the literature, this phenomenon is most commonly studied on iron (II), with 3d 6 electronic configuration.…”

Isomorphism between the electro-elastic modeling of the spin transition and Ising-like model with competing interactions: Elastic generation of self-organized spin states

“…Under the effect of external perturbations, such as a variation of temperature [25][26][27][28][29][30] , pressure [31][32][33][34][35][36] , light irradiation [36][37][38][39][40][41][42][43] , electric or magnetic field [44][45][46][47][48][49][50] , or chemical composition 36,[51][52][53] etc, the SCO solids may switch reversibly between HS and LS configurations leading to first-order or continuous (gradual)…”