Mn-based Heusler alloys have attracted significant research attention as half-metallic materials because of their giant magnetocr.ystalline anisotropy and magnetocaloric properties.We investigate the crystal structure...Mn-based Heusler alloys have attracted significant research attention as half-metallic materials because of their giant magnetocr.ystalline anisotropy and magnetocaloric properties.We investigate the crystal structure and magnetic properties of polycrystalline,[101]-oriented,and[100]-oriented Mn2-δ Sn prepared separately by arc melting,the Bridgeman method,and the flux method.All of these compounds crystallize in a Ni2 In-type structure.In the Mn2-δSn lattice,Mn atoms occupy all of the 2 a and a fraction of the 2 d sites.Site disorder exists between Mn and Sn atoms in the 2 c sites.In addition,these compounds undergo a re-entrant spin-glass-like transition at low temperatures,which is caused by frustration and randomness within the spin system.The magnetic properties of these systems depend on the crystal directions,which means that the magnetic interactions differ significantly along different directions.Furthermore,these materials exhibit a giant magnetocaloric effect near the Curie temperature.The largest value of maximum of magnetic entropy change(-△SM)occurs perpendicular to the[100]direction.Specifically,at 252 K,maximum-△SM is 2.91 and 3.64 J-kg-1K-1 for a magnetic field of 5 and7 T,respectively.The working temperature span over 80 K and the relative cooling power reaches 302 J/kg for a magnetic field of 7 T,which makes the Mn2-δSn compound a promising candidate for a magnetic refrigerator.展开更多
Let R be a commutative domain with 1 and Q(≠R)its field of quotients.In this note an R-module M is called w_(∞)-Warfield cotorsion if M∈WC∩P^(⊥)_(w_(∞)),where WC denotes the class of all Warfield cotorsion R-mod...Let R be a commutative domain with 1 and Q(≠R)its field of quotients.In this note an R-module M is called w_(∞)-Warfield cotorsion if M∈WC∩P^(⊥)_(w_(∞)),where WC denotes the class of all Warfield cotorsion R-modules and P_(w_(∞))the class of all w_(∞)-projective R-modules.It is shown that R is a PVMD if and only if all w-cotorsion R-modules are w_(∞)-Warfield cotorsion,and that R is a Krull domain if and only if every w-Matlis cotorsion strong w-module over R is a w_(∞)-Warfield cotorsion w-module.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11675006,51731001 and 11805006the National Key Research and Development Program of China under Grant Nos 2017YFA0206303,2016YFB0700901 and2017YFA0403701
文摘Mn-based Heusler alloys have attracted significant research attention as half-metallic materials because of their giant magnetocr.ystalline anisotropy and magnetocaloric properties.We investigate the crystal structure and magnetic properties of polycrystalline,[101]-oriented,and[100]-oriented Mn2-δ Sn prepared separately by arc melting,the Bridgeman method,and the flux method.All of these compounds crystallize in a Ni2 In-type structure.In the Mn2-δSn lattice,Mn atoms occupy all of the 2 a and a fraction of the 2 d sites.Site disorder exists between Mn and Sn atoms in the 2 c sites.In addition,these compounds undergo a re-entrant spin-glass-like transition at low temperatures,which is caused by frustration and randomness within the spin system.The magnetic properties of these systems depend on the crystal directions,which means that the magnetic interactions differ significantly along different directions.Furthermore,these materials exhibit a giant magnetocaloric effect near the Curie temperature.The largest value of maximum of magnetic entropy change(-△SM)occurs perpendicular to the[100]direction.Specifically,at 252 K,maximum-△SM is 2.91 and 3.64 J-kg-1K-1 for a magnetic field of 5 and7 T,respectively.The working temperature span over 80 K and the relative cooling power reaches 302 J/kg for a magnetic field of 7 T,which makes the Mn2-δSn compound a promising candidate for a magnetic refrigerator.
基金This work was partially supported by the Sichuan Science and Technology Program(2023NSFSC0074)the National Natural Science Foundation of China(11961050,12061001)Aba Teachers University(ASS20230106,20210403005,20220301016).
文摘Let R be a commutative domain with 1 and Q(≠R)its field of quotients.In this note an R-module M is called w_(∞)-Warfield cotorsion if M∈WC∩P^(⊥)_(w_(∞)),where WC denotes the class of all Warfield cotorsion R-modules and P_(w_(∞))the class of all w_(∞)-projective R-modules.It is shown that R is a PVMD if and only if all w-cotorsion R-modules are w_(∞)-Warfield cotorsion,and that R is a Krull domain if and only if every w-Matlis cotorsion strong w-module over R is a w_(∞)-Warfield cotorsion w-module.
