Low temperature magnetoresistance in La_1.32Sr_1.68Mn₂O₇ layered manganite under hydrostatic pressure

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• 作者：M. Kumaresavanji ; M.B. Fontes
• 关键词：Tunneling magnetoresistance ; Layered manganite ; Magnetic tunnel junction ; Hydrostatic pressure
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2010
• 出版时间：August 2010
• 年：2010
• 卷：322
• 期：16
• 页码：2355-2359
• 全文大小：531 K

文摘

The La_1.32Sr_1.68Mn₂O₇ layered manganite system has been studied by the low temperature electrical resistance and magnetoresistance under hydrostatic pressure up to 25 kbar. We have observe both, a Curie temperature (T_C) and a metal–insulator transition (T_MI) at 118 K in the ambient pressure. The applied pressure shifts the T_MI to higher temperature values and induces a second metal–insulator transition (T²_MI) at 90 K, in the temperature dependence of resistivity measurements. Also, the pressure suppresses the peak resistance abruptly at T_C. When an external field of 5 T is applied, we have observed a large negative magnetoresistance of 300 % at the transition temperature and a 128 % at 4.5 K. However, the increased pressure decreases the magnetoresistance ratio gradually. When the pressure reaches its maximum available value of 25 kbar, the magnetoresistance ratio decreases at a rate of 1.3 % /kbar. From our experimental results, the decrease of magnetoresistance ratio with pressure is explained by the pressure induced canted spin state which is not favor for the spin polarized intergrain tunneling in layered manganites.