Bose glass state in bulk (Nd,Eu,Gd)Ba₂Cu₃O _x with a high irreversibility field

(Nd,Eu,Gd)Ba₂Cu₃O_x (NEG123) bulk shows the high irreversibility properties. In order to clarify the origin of high irreversibility fields, the transport properties of NEG123 bulk with the high irreversibility field were investigated against high magnetic fields, temperatures, and field angles. We found that a dip in the angular dependent resistivity appears at B//c, originated to the correlated disorder along the c axis. In addition, the Bose glass phase was observed around B//c by the detailed analysis of the glass transition temperature and exponent. Therefore the Bose glass state plays an important role for realization of the high irreversibility field. It is suggested that new effective pinning centers correlated along the c axis are responsible for the high irreversibility field.