Effects of organic material on magnetoresistance in electron-doped double perovskite

Yafang Li ,Yu Liu,Yanming Zhang ,Jinfeng Wang

doi:10.1007/s10854-021-06390-8

Yafang Li , Yu Liu + Show 2 more

Open Access

https://doi.org/10.1007/s10854-021-06390-8

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Abstract

The Curie temperature of electron-doped Sr2FeMoO6 can be optimized significantly due to the band-filling effect, but accompanying an almost absent low-field magnetoresistance (LFMR), which is unfavorable to applications in the magnetoresistive devices operated at room temperature. Our previous works confirmed that, a remarkable enhanced LFMR was observed in Sr2FeMoO6 by modifying the grain boundary with insulating organic small molecules (glycerin, CH2OHCHOHCH2OH). However, in this work, modifying the grain boundary strength of the La0.5Sr1.5FeMoO6 with the insulating organic macromolecules (oleic acid, CH3(CH2)7CH=CH(CH2)7COOH) or small molecules (glycerin), both of them have negligible functions on the magnetoresistance (MR) behavior in La0.5Sr1.5FeMoO6. Contrary to the glycerin-modified Sr2FeMoO6, Sr2FeMoO6/oleic acid composites do not exhibit an obviously increased MR property. Based on the above experimental results and the related works, it is proposed that, maintaining high spin polarization of the carriers at the Fermi level and improving the tunneling process across the grain boundary using the suitable organic materials are decisive factors for optimizing the MR behavior in the similar electron-doped double perovskites.

Highlights

Due to its a half-metallic property with the 100% spin-polarization at the Fermi level, a high Curie temperature (TC) of ~415 K and remarkable large low-filed magnetoresistance (LFMR) behavior, double perovskite Sr2FeMoO6 (SFMO) has been paid a great deal of attention in views of its critical fundamental investigation values and immense potential technological applications for spintronic and magnetoresistive devices operated at room temperature [1]
The strength of magnetic coupling in SFMO double perovskite is mainly controlled by the carrier density at the Fermi level, so it indicates that doping electrons in the conduction band is an effective way to enhance TC [8,9,10,11,12,13,14]
The crystal structure of all prepared polycrystalline samples was detected by the X-ray diffraction (Fig. 1)

Summary

Introduction

Due to its a half-metallic property with the 100% spin-polarization at the Fermi level, a high Curie temperature (TC) of ~415 K and remarkable large low-filed magnetoresistance (LFMR) behavior, double perovskite Sr2FeMoO6 (SFMO) has been paid a great deal of attention in views of its critical fundamental investigation values and immense potential technological applications for spintronic and magnetoresistive devices operated at room temperature [1].It is well known that in an ideal SFMO double perovskite structure, the FeO6 and MoO6 octahedral arrange alternatively along the three axes of tetragonal structure with the Sr cations occupy the voids between them. The SFMO ceramic was soaked in organic matter, by the method directly, the resistivity was increased about 500 times and the LFMR value was effectively improved up to -29.5% at 10 K [28]. We infer that the method of preparing La0.5Sr1.5FeMoO6 (LSFMO)/organic matter composites could be used to eliminate the negative effect resulting from electrons doping in SFMO ceramics and optimize the LFMR effect while ensuring the magnetization.

Results

Conclusion