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