A large magnetic entropy change about twice as high as that of pure gadolin
ium metal near room temperature has been discovered in manganese perovskite
s La0.837Ca0.098Na0.038Mn0.987O3.00 (8.3 J(.)kg(-1.)K(-1), at 256 K) and La
0.822Ca0.096K0.043Mn0.974O3.00 (6.8 J(.)kg(-1.)K(-1), at 265 K) under a mag
netic field of 1.5 T. This phenomenon indicates that manganese perovskites
have potential applications for magnetic refrigerants in an extended temper
ature range even near room temperature.