Local magnetic moment in hydrogen-doped 1111-type iron pnictides probed by Electron Energy Loss Spectroscopy

Since superconductivity in Fe pnictides emerges adjacent to the antiferromagnetic phase, the magnetic properties have been intensively investigated by neutron scattering, NMR and muSR. Since their magnetic moments are strongly screened by itinerant electrons [1], it is needed to be probed in much faster process such as electron dynamics, for measuring the “bare” moment. Recently, it was proved that Electron Energy Loss Spectroscopy (EELS) is able to capture the bare moment in Ba(Fe$_{\mathrm{1-}}_{x}$Co$_{x})_{\mathrm{2}}$As$_{\mathrm{2}}$ [2]. In this study, we performed the EELS measurement on LaFeAsO$_{\mathrm{1-}}_{x}$H$_{x}$ with a double dome structure, and found that the Neel temperature and the critical temperature ($T_{\mathrm{N}}$, $T_{\mathrm{c}})$, especially in high-doped region, are related to the bare magnetic moment. In this talk, we also present the results in SmFeAsO$_{\mathrm{1-}}_{x}$H$_{x}$ and LaFePO$_{\mathrm{1-}}_{x}$H$_{x}$, and discuss the effects of the electron-doping and the local structure around Fe on the moment in the hydrogen-doped 1111-type iron pnictides [1] P. Hansmann et al., PRL 104, 197002 (2010). [2] C. Cantoni et al., Adv. Mater. 26, 6193 (2014).