NMR studies of the helical antiferromagnetic compound EuCo2P2

Abstract

In EuCo2P2, 4f electron spins of Eu2+ ions order antiferromagnetically below a Néel temperature. The magnetic structure below was reported to be helical with the helix axis along the c-axis from the neutron diffraction study. We report the results of 153Eu, 59Co and 31P nuclear magnetic resonance (NMR) measurements on EuCo2P2 using a single crystal and a powdered sample. In the antiferromagnetic (AFM) state, we succeeded in observing 153Eu, 59Co and 31P NMR spectra in zero magnetic field. The sharp 153Eu zero field NMR (ZF NMR) lines indicate homogeneous Eu ordered moment. The 59Co and 31P ZF NMR spectra showed an asymmetric spectral shape, indicating a distribution of the internal magnetic induction at each nuclear position. The AFM propagation vector k characterizing the helical AFM state can be determined from the internal magnetic induction at Co site. We have determined the model-independent value of the AFM propagation vector k distributed from (0, 0, 0.86)2π

Pressure-Induced Structural Phase Transition in EuNi2P2

“…There is a rich variety of compounds similar to the ThCr 2 Si 2 -type crystal ( I 4/ mmm ). Its unique tetragonal structure can accommodate a variety of atoms with large radius differences, which leads to its special structural and electromagnetic transitions that occur under high pressure. − According to previous works on high-pressure study of EuNi 2 P 2 , the crystal had no obvious structural change in the pressure range of 32–45 GPa. , Interestingly, this type of crystal often exhibits a transition to a collapsed tetragonal phase at high pressure, such as EuCo 2 As 2 , EuFe 2 As 2 , or EuCo 2 P 2 . In the phase transition, the abnormal sharp decrease in the c -axis parameter has attracted much attention. ,, The compressibility along the c -axis is higher than that along the a - and b -axes, and high-pressure-induced amorphization may even occur with significant compression along the c -axis .…”