Later he joined the Institute for Solid State Physics at the JÃ 1\/4 lich Research Centre , where he became a leading researcher of magnetism until he retired in 2004 . He later joined the Institute for Solid State Physics at Forschungszentrum JÃ 1\/4 lich , where he became a leading researcher in the field of thin film and multilayer magnetism until his retirement in 2004 .