Concentration dependence of magnetic characteristics in EuFe$_2$(As$_{\mathrm{1-x}}$P$_{\mathrm{x}}$)$_2$ single crystals*

In order to understand the structural and magnetic characteristics of EuFe$_{2}$(As$_{\mathrm{1-x}}$P$_{\mathrm{x}}$)$_{2}$, we have performed electron spin resonance (ESR) and magnetization measurements. The experimental results of the doping dependence of both measurements for the single crystal of EuFe$_{2}$(As$_{\mathrm{1-x}}$P$_{\mathrm{x}}$)$_{2}$ samples suggest the change of the exchange interaction and/or the anisotropy of Eu-site. The angular dependence of the ESR signal in the \textit{ab}-plane clearly shows the change of the in-plane anisotropy by the doping of P. The details will be discussed in the meeting.