Substitution of manganese by trivalent and tetravalent elements in the CMR perovskites Pr1-x(Ca, Sr)xMnO3
Substitution of manganese by trivalent and tetravalent elements in the CMR perovskites Pr1-x(Ca, Sr)xMnO3
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DOI：
10.1007/s002570050260
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发表时间：
1996-03
期刊：
影响因子：
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通讯作者：
A. Maignan;C. Martin;B. Raveau
中科院分区：
文献类型：
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作者：
A. Maignan;C. Martin;B. Raveau
研究了三价元素（M = In，Ga）和四价元素（M = Sn，Ti）分别取代Mn（III）和Mn（IV）对钙钛矿型巨磁电阻材料Pr 0.7Ca 0.2Sr 0.1MnO 3（I型）和Pr 0.5Sr 0.5MnO 3（II型）的影响。对于前一种化合物，无论是哪种元素，当取代元素含量增加时，分离铁磁金属态（FM）和顺磁非磁性（PSC）态的温度转变（Tmax或Tc）显著降低，低温下的饱和磁矩略有降低。对于这些I型钙钛矿的最大磁阻是实现为Pr0.7Ca0.2Sr0.1Mn0.99Ga0.01O3，达到600在127 K对275在151 K的原始样品的电阻比。这些结果表明，通过在锰位置上的M（IV）或M（III）取代来降低或增加空穴浓度，居里温度Tcis总是降低。与I型钙钛矿相反，两种不同的效果被证明为Pr0.5Sr0.5Mn1-xMxO 3取代的II型相取决于M价。一方面，对于M = Ga，In，当x增加时，反铁磁半导体（AFSC）态和PSC态以牺牲铁磁性为代价而被青睐。另一方面，对于M = Sn，Ti，低温AFSC状态趋于消失，并且对于x > 0.04，仅FM到PSC转变仍然存在，类似于在I型钙钛矿中观察到的。相应地，磁化强度随温度的变化曲线从典型的电荷有序态的钟形曲线演变为铁磁化合物的钟形曲线。讨论了I型和II型CMR钙钛矿化合价和d 0、d10电子组态的影响。
The substitution of trivalent (M = In, Ga) and tetravalent elements (M = Sn, Ti) for Mn(III) and Mn(IV) respectively has been studied in the colossal magnetoresistant (CMR) perovskites Pr0.7Ca0.2Sr0.1MnO3(type I) and Pr0.5Sr0.5MnO3(type II). For the former compound, whatever the element, the temperature transition (Tmaxor Tc) separating the ferromagnetic metallic (FM) state and the paramagnetic semiconductinc (PSC) state decreases dramatically when the substituted element content is increased, the saturated magnetic moment at low temperature being slightly decreased. For these type I perovskites the maximum magnetoresistance is achieved for Pr0.7Ca0.2Sr0.1Mn0.99Ga0.01O3, reaching a resistance ratio of 600 at 127 K against 275 at 151 K for the pristine sample. These results show that by decreasing or increasing the hole concentration via M(IV) or M(III) substitutions on the manganese site the Curie temperature Tcis always decreased. In contrast to the type I perovskites, two different effects are evidenced for the Pr0.5Sr0.5Mn1-xMxO3substituted type II phases depending on the M valence. On one hand for M = Ga, In when x increases the antiferromagnetic semiconducting (AFSC) state and the PSC state are favoured at the expense of ferromagnetism. On the other hand for M = Sn, Ti the low temperature AFSC state tends to disappear and for x > 0.04 only a FM to PSC transition still exits similarly to that observed in type I perovskites. Correspondingly the magnetization versus temperature curves evolve from the bell shape curve typical of the charge ordering state to that of a ferromagnetic compound. The effect of valence and d0, d10electronic configurations in both type I an II CMR perovskites is discussed.