wherein R1 stands for at least one element selected from the group consisting of {TAIL ~ La}, Nd, Sm, Eu and Gd and x and d are {HEAD ~ numbers} as follows: 
wherein R1 stands for at least one element selected from the group consisting of { TAIL ~ La } , Nd , Sm , Eu and Gd and x and d are { HEAD ~ numbers } as follows :
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH