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arXiv 0806.1599cond-mat.str-el
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双层锰氧化物(La(1-z)Pr(z))1.2Sr1.8Mn2O7的磁序:内禀性质和共生体的作用

Magnetic order in double-layer manganites (La(1-z)Pr(z))1.2Sr1.8Mn2O7: intrinsic properties and role of the intergrowths

G. Allodi, M. Bimbi, R. De Renzi, C. Baumann, M. Apostu, R. Suryanarayanan, A. Revcolevschi

摘要:

本文报道了用宏观磁测量和局部磁探针(muSR,55 MnNMR)对双层锰氧化物系列(La(1-z)Pr(z))1.2Sr1.8Mn2O7(0 <= z <= 1)单晶的研究。μ子和NMR表明,在非铁磁成分(z >= 0.6)的反铁磁有序的基态,而更温和的Pr取代(0.2 <= z <= 0.4)诱导铁磁相内的自旋重取向转变。在{Tc,TN} < T <250 K时,所有组分都有很大的磁化率。从55 Mn NMR光谱,这样的响应是明确地分配到铁磁伪立方相(La(1-z)Pr(z))(1-x)Sr(x)MnO 3的共生体,与总体积分数估计为0.5-0.7%,从磁力。这些夹杂物的磁矩与周围的(La(1-z)Pr(z))1.2Sr1.8Mn2O7相的磁矩的耦合提供了证据,如在细分散杂质的情况下。我们认为,无处不在的共生相可能会发挥作用,在显着的一阶字符的磁性转变和变磁性的双层锰氧化物的Tc以上的报告。

英文摘要:

We report on an investigation of the double-layer manganite series (La(1-z)Pr(z))1.2Sr1.8Mn2O7 (0 <= z <= 1), carried out on single crystals by means of both macroscopic magnetometry and local probes of magnetism (muSR, 55Mn NMR). Muons and NMR demonstrate an antiferromagnetically ordered ground state at non-ferromagnetic compositions (z >= 0.6), while more moderate Pr substitutions (0.2 <= z <= 0.4) induce a spin reorientation transition within the ferromagnetic phase. A large magnetic susceptibility is detected at {Tc,TN} < T < 250K at all compositions. From 55Mn NMR spectroscopy, such a response is unambiguously assigned to the intergrowth of a ferromagnetic pseudocubic phase (La(1-z)Pr(z))(1-x)Sr(x)MnO3, with an overall volume fraction estimated as 0.5-0.7% from magnetometry. Evidence is provided for the coupling of the magnetic moments of these inclusions with the magnetic moments of the surrounding (La(1-z)Pr(z))1.2Sr1.8Mn2O7 phase, as in the case of finely dispersed impurities. We argue that the ubiquitous intergrowth phase may play a role in the marked first-order character of the magnetic transition and the metamagnetic properties above Tc reported for double-layer manganites.

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