Long-Range Spin-Selective Transport in Chiral Metal–Organic Crystals with Temperature-Activated Magnetization

Abstract

Room-temperature, long-range (300 nm), chirality-induced spin-selective electron conduction is found in chiral metal–organic Cu(II) phenylalanine crystals, using magnetic conductive-probe atomic force microscopy. These crystals are found to be also weakly ferromagnetic and ferroelectric. Notably, the observed ferromagnetism is thermally activated, so that the crystals are antiferromagnetic at low temperatures and become ferromagnetic above ∼50 K. Electron paramagnetic resonance measurements and density functional theory calculations suggest that these unusual magnetic properties result from indirect exchange interaction of the Cu(II) ions through the chiral lattice.

Temperature Dependence of Charge and Spin Transfer in Azurin

“…As the Cu(I/II)–ligand vibration(s) proceeds, it generates charge displacements in the chiral ligand’s electron cloud, and these are accompanied by partial spin polarization of the electron cloud. 51 Because the amplitude of the motion is small at low temperature and is nearly harmonic, the local fluctuating B vib field is small. At higher temperatures ( Figure 4 B), larger displacements occur along the vibrational coordinate, and they access more anharmonic regions of the vibrational coordinate between the copper and its chiral ligands, giving rise to a net local magnetic polarization.…”

Metal Organic Spin Transistor

“…In a recent work, these crystals were shown to have good conduction and both ferromagnetic and ferroelectric properties at room temperature. 13 As a demonstration of their material properties, we showed that this material can be used to fabricate spintronic devices with multilevel memory 34 as well as a spin transistor device. 35 This spin transistor device also exhibits nonlinear memristive behavior utilized as a universal memory, and it enables logic operations.…”

“…It was previously found that conduction through the crystals is spin selective at room temperatures, due to the CISS effect. 13 In that reference, the coercive field is measured at different temperatures and was found to be about 200 Oe at room temperatures. Since the excitation by circularly polarized light results in exciting in a one spin direction, following the excitation, there is an electron in the excited state with one specific spin and the hole in the ground state has the same specific spin.…”

The Internal Field in a Ferromagnetic Crystal with Chiral Molecular Packing of Achiral Organic Radicals

“…Chirality [14] has recently been used in designing new chiral catalysts [15], developing organic spin filters [16], and investigating spin-dependent tunnelling through chiral molecules [17][18][19]. It has an important role in photochemistry that may have been important in the origin of life [20].…”