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作 者:张爱梅[1] 朱佳佳 方天诚 潘茜茜 ZHANG Aimei;ZHU Jiajia;FANG Tiancheng;PAN Xixi(College of Science,Hohai University,Nanjing 210093,China)
机构地区:[1]河海大学理学院,南京210093
出 处:《无机材料学报》2023年第2期148-154,共7页Journal of Inorganic Materials
基 金:国家自然科学基金(11404091);江苏省自然科学基金(BK20140839)。
摘 要:钙钛矿锰氧化物La_(1-x)Sr_(x)MnO_(3)(LSMO)作为一种代表性庞磁阻材料,在磁传感器等领域具有广阔的应用前景,但在低磁场和室温下很难获得显著的庞磁阻效应。为提高LSMO磁电阻效应和转变温度,本研究采用传统固相反应法制备了La_(0.8)Sr_(0.2)Mn_(1-x)Al_(x)O_(3)(0≤x≤0.25)(LSMAO)多晶样品,并系统分析了Al^(3+)掺杂对LSMO电输运性质和磁电阻效应的影响。X射线衍射(XRD)图谱表明LSMAO样品具有单一的菱方结构,属于R3C空间群。电输运性质研究发现,样品的电阻率随Al^(3+)的掺杂呈指数型上升,且外加磁场使金属-绝缘体转变温度有所提高。这可能是由于Al^(3+)稀释了Mn^(3+)/Mn^(4+)离子网络,在减少载流子数量的同时增加了磁无序。此外,LSMAO陶瓷的导电机理随Al^(3+)的掺杂从小极化子模型(Small polaron hopping model,SPH)转变成变程跳跃模型(Variable range hopping model,VRH),说明非磁性的Al^(3+)抑制了铁磁团簇间的载流子交换,使得小极化子热激活近邻跃迁过程被抑制。LSMAO的磁电阻效应从21.03%(x=0)增大到59.71%(x=0.25),证明Al^(3+)掺杂可有效增强LSMAO的磁电阻效应。As a colossal magnetoresistance material,the perovskite manganese oxide La_(1-x)Sr_(x)MnO_(3)(LSMO)has broad application prospects in magnetic sensors and other fields.However,it is difficult to obtain a significant colossal magnetoresistance effect at a low magnetic field at room temperature.To improve its magnetoresistance effect and transition temperature,La_(0.8)Sr_(0.2)Mn_(1-x)Al_(x)O_(3)(0≤x≤0.25)(LSMAO)polycrystalline samples were prepared by traditional solid-state reaction method in present work.Effects of Al^(3+)doping on the electrical transport property and magnetoresistance of LSMO were systematically analyzed.The X-ray diffraction(XRD)results indicate that all samples crystallize in a single rhombohedral structure with the space group of R3C.Result of electrical transport property shows that resistivity of the samples increases exponentially with the increment of Al^(3+)doping amount,and the metal-insulator transition temperature is increased by an external magnetic field.This phenomenon may be attributed to dilution of the Mn^(3+)/Mn^(4+)ions network by Al^(3+),which increases the magnetic disorder but reduces the number of carriers.In addition,the conduction mechanism of LSMAO ceramics change from the small polaron hopping model(SPH)to the variable range hopping model(VRH)after doping of Al^(3+),reflecting that the non-magnetic Al^(3+)weakens the carrier exchange between the ferromagnetic clusters.As a result,the thermally activated neighbor transition of small polarons is suppressed.Magnetoresistance effect of LSMAO is enhanced from 21.03%to 59.71%with x increasing from 0 to 0.25,which proves that the doping of Al^(3+)can effectively enhance the magnetoresistance effect of LSMAO.
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