Background:structures and facts a P//c a 600 1.10 0.8 (-6 nwa) (J mol-1 K-2) Specific heat/temperature 400 1.08 0.6 15K 9K 200 0.4 1.06 0 b 600 400 400 200 200 9 15K 0 0 0 20 30 40 0 Temperature(K) 0 Magnetic field (T) Kimura,Annu.Rev.Mater.Res.37,387,2007 Background: structures and facts Kimura, Annu. Rev. Mater. Res.37, 387, 2007