Enhanced temperature coefficient of resistance and magnetoresistance of Co-doped La0.67Ca0.33MnO3 polycrystalline ceramics. Issue 1 (1st January 2022)

• Record Type: Journal Article
• Authors: Li, Yule; Li, Junfeng; Chen, Qinghua; Zhang, Hui; Liu, Xiang; Chen, Qingming
• Is Part Of: Ceramics international. Volume 48:Issue 1(2022)
• Page Start: 407
• Page End: 414
• Publication Date: 2022-01-01
• Subjects: La0.67Ca0.33Mn1-xCoxO3 -- Temperature coefficient of resistance (TCR) -- Magnetoresistance (MR) -- Sol-gel method; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2021.09.116
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Recently, La0.67 Ca0.33 MnO3 has garnered significant research attention due to its peculiar physical properties, such as colossal magnetoresistance and metal insulator transitions. The practical applications of these materials are mainly determined by the temperature coefficient of resistance (TCR) and magnetoresistance (MR). As a mature synthesis route, the sol-gel method can prepare high-quality ceramic targets. Herein, using methanol as a solvent, La0.67 Ca0.33 Mn1-x Cox O3 (0 ≤ x ≤ 0.06) polycrystalline ceramics are prepared using the sol-gel method and the influence of Co doping on electrical and magnetic properties is systematically studied. Co doping increases the grain size, and is helpful to improve TCR and MR. In addition, with increased Co doping, the double exchange is weakened, and the ferromagnetism is depressed, which leads to a decrease in TMI . The results reveal that the TCR and MR can be optimized by tuning the Co content. For instance, we have achieved a TCR value of 44.2% · K −1 at x = 0.02 and an MR value of 76.3% at x = 0.04, showing the promise of Co-doped La0.67 Ca0.33 MnO3 ceramics in a wide array of applications, such as bolometers and magnetic sensors. Graphical abstract: Furthermore, we have measured the ZFC and FC values under a magnetic field of 0.01 T. The results reveal that the as-prepared polycrystalline ceramics exhibited the FM-PM transition. The ZFC and FC curves merged at a temperature higher than TC, followed by a sudden decrease. One should note that the movement of magnetic domains along the direction of magnetic field is restricted because the pinning of domain walls leads to insufficient magnetization. Therefore, we can infer that the application of a magnetic field helps overcome the fixation of domain walls. The ZFC and FC curves separate at the irreversible temperature (Tirr ) close to TC, and the difference significantly increases with the decrease of temperature, which is mainly caused by the hysteresis effect [35, 36].