La 0.9 Eu 0.1 ) 4/3 Sr 5/3 Mn 2 O 7 polycrystalline sample was prepared by solid state reaction method. The magnetic and magnetocaloric properties have been studied. The competition between FM and AFM interactions was observed at low temperature range, and the coexistence of FM and PM was found in the temperature range of T c 3D -T c 2D for this compound. In addition, the magnetic entropy change under 1 T magnetic field is up to 1.69 J/(kg K), which suggests that such materials may be applied to magnetic refrigeration in the temperature range of liquid hydrogen.

The polycrystalline samples of two-layered perovskite manganites (La1-xGdx)4/3Sr5/3Mn2O7 (x=0, 0.025) are prepared by traditional solid state reaction method. X-ray diffraction measurements show that both samples are of the Sr3Ti2O7 -type tetragonal phase (space groups I4/mmm). Magnetic measurements show that Gd3+ doping reduces the magnetic transition temperature (TC3D) and magnetization (M) of the doped sample (La0.975Gd0.025)4/3Sr5/3Mn2O7, which is because Gd3+ doping induces lattice distortion and change the lattice constant, and subsequently weakens the double exchange interactions. It is found from electron spin resonance measurements that short-range ferromagnetic clusters appear in the paramagnetic background of both samples at temperatures TC3DTTC3DT0.975Gd0.025)4/3Sr5/3Mn2O7 has a higher resistance. This is because Gd3+ doping reduces the localization length of carriers, and makes conducting carriers absorb more energy to overcome the bound potentials in the lattice.