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arXiv 1208.0929cond-mat.supr-concond-mat.str-el
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Ni掺杂对Eu0 .5K0.5Fe2As2磁性和超导电性的影响

Effect of Ni-doping on magnetism and superconductivity in Eu0.5K0.5Fe2As2

Anupam, V. K. Anand, P. L. Paulose, S. Ramakrishnan, C. Geibel, Z. Hossain

摘要:

本文通过对Eu_(0.5)K_(0.5)Fe_(1-x)Ni_(0.5)As_(0.5)(x = 0,0.03,0.05,0.08和0.12)化合物的直流和交流磁化率、电阻率和比热的测量,系统地研究了Ni掺杂对Eu_(0.5)K_(0.5)Fe_(22)As_2的磁性和超导性的影响。Eu0.5K0.5Fe2As2具有超导电性,其超导转变温度Tc高达33 K。Ni的掺杂导致超导转变温度的快速下降,3%Ni的掺杂使超导转变温度降低到23 K,而8%Ni的掺杂使超导转变温度降低到1.8K以下。在Tm ~ 6 K范围内,掺3%Ni的Eu_(0.5)K_(0.5)(Fe_(0.97)Ni_(0.03))_2As_2样品中,超导电性与Eu ~(2+)磁矩的短程有序性共存。Ni掺杂抑制了Eu0.5K0.5(Fe0.92Ni0.08)2As 2和Eu0.5K0.5(Fe0.88Ni0.12)2As 2的超导电性,并伴随着长程反铁磁有序的出现,TN分别为8.5 K和7 K. x = 0.08和0.12的样品的温度和磁场相关的磁性测量反映的可能性的螺旋磁有序的Eu 2时刻。我们怀疑Eu自旋的helimagnetism可能是负责的超导电性的破坏已被观察到在Co掺杂EuFe 2As 2。在x = 0.08的电阻率数据中看到的最显著的特征是异常的再现,推测是由于在60 K左右的自旋密度波跃迁。这可以归因于电子(Fe位的Ni掺杂)对空穴(Eu位的K掺杂)的补偿。当x = 0.12时,自旋密度波的异常进一步移动到200 K,此时电子掺杂几乎补偿了体系中的空穴。

英文摘要:

The effect of Ni-doping on the magnetism and superconductivity in Eu0.5K0.5Fe2As2 has been studied through a systematic investigation of magnetic and superconducting properties of Eu0.5K0.5(Fe1-xNix)2As2 (x = 0, 0.03, 0.05, 0.08 and 0.12) compounds by means of dc and ac magnetic susceptibilities, electrical resistivity and specific heat measurements. Eu0.5K0.5Fe2As2 is known to exhibit superconductivity with superconducting transition temperature Tc as high as 33 K. The Ni-doping leads to a rapid decrease in Tc; Tc is reduced to 23 K with 3% Ni-doping, and 8% Ni-doping suppresses the superconductivity to below 1.8 K. In 3% Ni-doped sample Eu0.5K0.5(Fe0.97Ni0.03)2As2 superconductivity coexists with short range ordering of Eu2+ magnetic moments at Tm ~ 6 K. The suppression of superconductivity with Ni-doping is accompanied with the emergence of a long range antiferromagnetic ordering with TN = 8.5 K and 7 K for Eu0.5K0.5(Fe0.92Ni0.08)2As2 and Eu0.5K0.5(Fe0.88Ni0.12)2As2, respectively. The temperature and field dependent magnetic measurements for x = 0.08 and 0.12 samples reflect the possibility of a helical magnetic ordering of Eu2 moments. We suspect that the helimagnetism of Eu spins could be responsible for the destruction of superconductivity as has been observed in Co-doped EuFe2As2. The most striking feature seen in the resistivity data for x = 0.08 is the reappearance of the anomaly presumably due to spin density wave transition at around 60 K. This could be attributed to the compensation of holes (K-doping at Eu-site) by the electrons (Ni-doping at Fe site). The anomaly associated with spin density wave further shifts to 200 K for x = 0.12 for which the electron doping has almost compensated the holes in the system.

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