Uniaxial Pressure Effect on the Magnetic Ordered Moment and Transition Temperatures in BaFe2-xTxAs2 (T=Co,Ni)
David W. Tam, Yu Song, Haoran Man, Sky C. Cheung, Zhiping Yin, Xingye Lu, Weiyi Wang, Benjamin A. Frandsen, Lian Liu, Zizhou Gong, Takashi U. Ito, Yipeng Cai, Murray N. Wilson, Shengli Guo, Keisuke Koshiishi, Wei Tian, Bassam Hitti, Alexandre Ivanov, Yang Zhao, Jeffrey W. Lynn, Graeme M. Luke, Tom Berlijn, Thomas A. Maier, Yasutomo J. Uemura, Pengcheng Dai
We use neutron diffraction and muon spin relaxation to study the effect of uniaxial pressure on the paramagnetic-to-antiferromagnetic phase transition (TN) in BaFe2As2 and superconducting BaFe1.915Ni0.085As2. In a local moment picture, the uniaxial pressure necessary to detwin the sample may change TN due to pressure-induced orthorhombic lattice distortion, but is not expected to increase the ordered moment of the system. While this is indeed the case for BaFe2As2, we find that the magnetic moment in BaFe1.915Ni0.085As2 increases by as much as 20% under modest uniaxial pressures. These results are consistent with calculations of the spin susceptibility within the random-phase approximation (RPA), suggesting that Fermi surface nesting of itinerant electrons remains a crucial aspect of magnetism in iron pnictides near optimal superconductivity.