1205.0604 (Long Ma et al.)

Quenched Fe Moment in the Collapsed Tetragonal Phase of
Ca$_{1-x}$Pr$_{x}$Fe$_2$As$_2$    [PDF]

Long Ma, G. F. Ji, J. Dai, S. R. Saha, J. Paglione, Weiqiang Yu

We report $^{75}$As NMR studies on single crystals of rare-earth doped iron pnictides superconductor Ca$_{1-x}$Pr$_{x}$Fe$_{2}$As$_{2}$ ($x$=0.075 and 0.15). The $^{75}$As spectra show a chemical pressure effect with doping and a first order structure transition to the collapsed tetragonal phase upon cooling. A sharp drop of the Knight shift is seen below the structural transition, whereas $1/T_1$ is strongly enhanced at low-temperatures. These evidences indicate quenching of Fe local magnetism and short-range ordering of Pr$^{3+}$ moment in the collapsed tetragonal phase. The quenched Fe moment through structure collapse suggests a strong interplay of structure and magnetism, which is important for understanding the nature of the collapsed tetragonal phase.

View original: http://arxiv.org/abs/1205.0604