We have systematically measured resistivity, susceptibility and specific heat under different magnetic fields (H) in Eu1−xLaxFe2As2 single crystals. It is found that a metamagnetic transition from A-type antiferromagnetism to ferromagnetism occurs at a critical field for magnetic sublattice of Eu2+. The jump of specific heat is suppressed and shifts to low temperature with increasing H up to the critical value, then shifts to high temperature with further increasing H. Such behavior supports the metamagnetic transition. Detailed H-T phase diagrams for x=0 and 0.15 crystals are given, and possible magnetic structure is proposed. Magnetoresistance measurements indicate that there exists a strong coupling between local moment of Eu2+ and charge in Fe-As layer. These results are very significant to understand the underlying physics of FeAs superconductors.
@article{arxiv.0808.2247,
title = {Magnetic phase diagram in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ single crystals},
author = {T. Wu and G. Wu and H. Chen and Y. L. Xie and R. H. Liu and X. F. Wang and X. H. Chen},
journal= {arXiv preprint arXiv:0808.2247},
year = {2015}
}