Molecular and Interfacial Adjustment of Magnetoresistance in Organic Spin Valves Using Isoindigo-Based Polymers

Abstract

The organic interlayer is a crucial part in organic spin valves (OSVs), and its molecular structure has an important effect on the device performance. In this work, we utilized conjugated polymers based on isoindigo derivatives (PIID-TVTCN, PAIID-TVTCN, and PFIID-TVTCN) to fabricate OSVs and studied the dependence of the performance on the polymer structure. Positive magnetoresistance (MR) was obtained in OSVs with 40 nm polymeric thin films. Under the same conditions, the introduction of a pyridine nitrogen into the conjugated skeleton (PAIID-TVTCN) induced an increased MR value, while fluorine substitution in the isoindigo unit resulted in no change in MR. The relationship between structure and performance was further clarified. However, the MR was negative in OSVs with 25 nm polymeric thin films but flipped to positive when an AlO x film was inserted under the Co electrode. Thus, the negative MR was attributed to a synergistic effect between tunneling transport and interfacial coupling. The results highlight the effects of the polymer structure and thickness as well as the insertion of a layer of AlO x on the performance of OSVs and are also the first for this kind of multidimensional functionalized modulation of MR in polymeric-based OSVs.

Room-temperature magnetoresistance in Ni78Fe22/C8-BTBT/Ni78Fe22 nanojunctions fabricated from magnetic thin-film edges using a novel technique

“…Such incongruence between the MR curves and magnetization states has also been reported in other studies. 1,7,9,14 For example, in Alq 3 -based MR devices, the top electrode (Co) and bottom electrode (LSMO) showed coercivities of 150 and 30 Oe, respectively, which are not in good agreement with the values 170 and 70 Oe, respectively, estimated from the observed MR effect. 1 In another study, the MR effect was observed in Ni/benzene-1,4-dithiol (BDT)/Ni single molecular junctions using mechanically controllable break junction (BJ) method.…”

“…Typical molecular spintronic devices are organic spin valves (OSVs) which consist of organic molecules sandwiched between two magnetic layers. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] These types of devices show a large magnetoresistance (MR) effect. The resistance of such devices changes according to the conguration of the magnetization vectors in both magnetic layers adjacent to the molecular layer.…”

“…1,2,4,8,11,12,15,17 By contrast, recent studies have reported that high-mobility molecules, such as P(NDI2OD-T2) ($0.2-0.85 cm 2 V −1 s −1 ) 31 and PTDCNTVT-320 ($0.8-1.46 cm 2 V −1 s −1 ), 32 can be used in OSVs. 6,9,14 Thus, C8-BTBT could be potentially applicable to high-performance molecular spintronic devices. Such excellent devices will be scaled down for future integration, where one recorded bit may even reach the nanometer scale.…”

Magnetoresistance in Organic Spin Valves Based on Acid‐Exfoliated 2D Covalent Organic Frameworks Thin Films

“…electrode and the MR curve of OSV device could be assigned to the interfical hybrid states between Co electrode and the organic active layer, which affected the coercive behavior of Co electrode. [26,30] It was noteworthy that the MÀ H curve depicted in Figure S17 demonstrated no evidence of FM behavior for the reactivated COF powder. Therefore, during the scanning of external magnetic field from + 2000 to À 2000 Oe, the resistance of the OSVs was initially switched at a low magnetic field corresponding to the coercive field of LSMO, and then converted to a large resistivity state under high fields, and vice versa (Figure 4c).…”

Synthetic strategies, molecular engineering and applications of semiconducting polymers based on diarylethylene units in electronic devices

“…82 Likewise, the positive MR values were also obtained in OSVs based on P88–P90 . 142 Yu and co-workers synthesized P91–P94 by introducing a cyano group on the double bonds of TVT, and investigated the structure–property relationships in OFETs and OSVs. 143 The results suggested that the introduction of pyridine nitrogen atoms enhanced the electron mobilities of OFETs and MR values of OSVs, whereas the extension of alkyl chain branching points lowered the MR values.…”