Kawanaka H, Yokoyama M, Noguchi A, Bando H, Nishihara Y
National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan.
J Phys Condens Matter. 2009 Jul 22;21(29):296002. doi: 10.1088/0953-8984/21/29/296002. Epub 2009 Jul 3.
The effect of Mn substitution in paramagnetic metal CaRuO(3) was studied by magnetization and neutron diffraction measurements. Development of ferromagnetic order is observed for x≥0.2 in CaRu(1-x)Mn(x)O(3). For the sample with x = 0.4, the Curie temperature of ∼160 K is obtained from the Arrott plot and the ratio of effective moment and saturation moment P(eff)/M(0) is estimated to be ∼4.8. We further found that the magnetization is significantly suppressed with decreasing temperature T below ∼90 K. In the neutron diffraction experiment at T = 15 K, we observed the evolution of a magnetic Bragg peak originating from the G-type antiferromagnetic order as well as the ferromagnetic one. This strongly suggests that both ferromagnetic and antiferromagnetic states are coexistent with each other at low temperatures. In the M(T)(0)(2) against T(2) plot (here, M(T)(0) is a spontaneous magnetization estimated from the Arrott plot), M(T)(0)(2) linearly increases with decreasing T(2) in the ferromagnetic region between ∼90 and 160 K. The ferromagnetic properties of the CaRu(1-x)Mn(x)O(3) system (x≤0.5) are well explained in terms of spin fluctuation theory based on the itinerant electron model rather than the localized spin model.
通过磁化和中子衍射测量研究了顺磁性金属CaRuO₃中Mn取代的影响。在CaRu₁₋ₓMnₓO₃中，当x≥0.2时观察到铁磁序的发展。对于x = 0.4的样品，从阿罗特图获得约160 K的居里温度，有效磁矩与饱和磁矩之比P(eff)/M(0)估计约为4.8。我们还发现，当温度T降至约90 K以下时，磁化强度会显著受到抑制。在T = 15 K的中子衍射实验中，我们观察到源于G型反铁磁序以及铁磁序的磁布拉格峰的演变。这强烈表明，铁磁态和反铁磁态在低温下相互共存。在M(T)(0)²对T²的图中（这里，M(T)(0)是根据阿罗特图估计的自发磁化强度），在约90至160 K的铁磁区域中，M(T)(0)²随着T²的降低而线性增加。基于巡游电子模型而非局域自旋模型的自旋涨落理论很好地解释了CaRu₁₋ₓMnₓO₃体系（x≤0.5）的铁磁性质。
