Spin Rectification and Electrically Controlled Spin Transport in Molecular-Ferroelectrics-Based Spin Valves

Abstract

We report a spin-rectification effect in a spin-valve structure consisting of ferroelectric croconic acid (C 5 H 2 O 5 ) sandwiched between ferromagnetic electrodes La 0.7 Sr 0.3 MnO 3 and Co, which can be switched between a high-resistance (off ) and a low-resistance (on) state by a poling voltage. In the off state, the magnetoresistance (MR) sign reverses with the measurement voltage with a 0.1-V offset, suggesting a spin-rectification behavior, while in the on state the MR remains negative. These observations can be understood in terms of electrically controlled interfacial energy-band alignment either from the electrostatic effect or from the interfacial redox process. The observed spin-rectification effect suggests the possibility of diodelike devices for spin-polarized current.

Manipulation of Magnetic Properties and Magnetoresistance in Co/Cu/γ′-Fe4N/Mica Flexible Spin Valves via External Mechanical Strains

“…Figure a–c show the MR– H curves of Co/Cu/γ′-Fe 4 N flexible SPVs with different FM and NM thicknesses at 2 K, where the in-plane H is parallel to I . MR– H signals are similar to those of La 0.67 Sr 0.33 MnO 3 -based organic and inorganic SPVs. , Unlike the MR signs of flexible SPVs reported previously, , a negative MR is observed in Co/Cu/γ′-Fe 4 N flexible SPVs, which indicates a trend of resistance drop with a decrease of H . Scattering spin asymmetry coefficients of adjacent FM layers are responsible for the signs of MR. A positive MR signal is obtained for adjacent FM layers with the same spin polarization, and a negative MR signal is the result of the opposite spin polarization of adjacent FM layers .…”

“…Fast Fourier transform (FFT) and inverse fast Fourier transform Figure 2d shows the measurement geometry of flexible SPVs. Figure 2a 41,42 Unlike the MR signs of flexible SPVs reported previously, 43,44 a negative MR is observed in Co/Cu/γ′-Fe 4 N flexible SPVs, which indicates a trend of resistance drop with a decrease of H. Scattering spin asymmetry coefficients of adjacent FM layers are responsible for the signs of MR. A positive MR signal is obtained for adjacent FM layers with the same spin polarization, and a negative MR signal is the result of the opposite spin polarization of adjacent FM layers. 45 The scattering spin asymmetry coefficients in [Co/Cu] 10 multilayers have been reported, and the spin-down electrons show stronger scattering at the Co/Cu(111) interface in comparison to spin-up electrons due to the large difference in electronic state symmetry between Co and Cu.…”

Organic ferroelectric croconic acid: a concise survey from bulk single crystals to thin films

“…Furthermore, Yin et al 69 have taken a step toward integrating CA thin films into a spin valve device as a ferroelectric spacer and demonstrate spintronic applications of CA. With a 6 nm thick film of CA and 1 nm SiO 2 as the spacer and with Co and lanthanum strontium manganite (LSMO) as the magnetic electrodes, they have shown the voltage control of the spin transport properties, such as magnetoresistance (MR), of the spin valve device and shown spin rectification occurring at the Co/CA interface.…”

“…This nanoscopic detection of switching currents can provide deeper insights into the fundamental processes associated with the polarization reversal and pave the way toward exploring the kinetics of polarization reversal processes in CA thin films. 132 Furthermore, Yin et al 69 have taken a step toward integrating CA thin films into a spin valve device as a ferroelectric spacer and demonstrate spintronic applications of CA. With a 6 nm thick film of CA and 1 nm SiO 2 as the spacer and with Co and lanthanum strontium manganite (LSMO) as the magnetic Fig.…”

“…Following the discovery of ferroelectricity in the crystal form of CA, several groups have started working on various aspects of the powder, [48][49][50] bulk single crystal, [51][52][53][54][55][56][57][58][59] self-assembled co-crystal, 60,61 composite film 62 and thin film [63][64][65][66][67][68][69][70] forms of the molecule. Most of the studies have focused on the ferroelectric and optical properties of the macroscopic crystals of CA.…”