Enhanced magnetocaloric effect material

Abstract

A magnetocaloric effect heterostructure having a core layer of a giant magnetocaloric material and an elastically stiff material layer coated on at least one surface of the magnetocaloric material layer. The elastically stiff material layer restricts volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect composite powder including a plurality of core particles of a giant magnetocaloric material. Each of the core particles is encapsulated within a coating of elastically stiff material that restricts volume changes of the core particles during application of a magnetic field thereto. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with an elastically stiff material. The elastically stiff material restricts volume changes of the magnetocaloric material during application of a magnetic field thereto.

1 . A magnetocaloric effect heterostructure comprising: 
 a core layer of a giant magnetocaloric material; and    an elastically stiff material layer coated on at least one surface of said core layer, said elastically stiff material layer restricting volume changes of said core layer during application of a magnetic field to said heterostructure.    
     
     
         2 . A magnetocaloric effect heterostructure as defined in  claim 1 , wherein said core layer of giant magnetocaloric material is a compound of Gd 5 (Si 1-x  Ge x ) 4 .  
     
     
         3 . A magnetocaloric effect heterostructure as defined in  claim 1 , wherein said elastically stiff coating layer is a low-coercivity, high-magnetization material.  
     
     
         4 . A magnetocaloric effect heterostructure as defined in  claim 3 , wherein said coating layer of low-coercivity, high-magnetization material comprises an element selected from the group consisting of iron, cobalt, nickel and magnetic oxides.  
     
     
         5 . A magnetocaloric effect heterostructure as defined in  claim 1 , wherein said elastically stiff material layer is coated on opposite surfaces of said core layer.  
     
     
         6 . A magnetocaloric effect heterostructure as defined in  claim 1 , wherein said elastically still material layer substantially encapsulates said core layer.  
     
     
         7 . A magnetocaloric effect heterostructure as defined in  claim 1 , wherein said coating layer is applied to said core layer using a chemical vapor deposition process.  
     
     
         8 . A magnetocaloric effect composite powder comprising a plurality of core particles of a giant magnetocaloric material, each of said core particles being encapsulated within a coating of elastically stiff material, said elastically stiff coating restricting volume changes of said core particles during application of a magnetic field thereto.  
     
     
         9 . A magnetocaloric effect composite powder as defined in  claim 8 , wherein said giant magnetocaloric material of said core particles is a compound of Gd 5 (Si 1-x  Ge x ) 4 .  
     
     
         10 . A magnetocaloric effect composite powder as defined in  claim 8 , wherein said elastically stiff coating is a low-coercivity, high-magnetization material.  
     
     
         11 . A magnetocaloric effect composite powder as defined in  claim 10 , wherein said coating of low-coercivity, high-magnetization material comprises an element selected from the group consisting of iron, cobalt, nickel and magnetic oxides.  
     
     
         12 . A magnetocaloric effect composite powder as defined in  claim 8 , wherein said core particles are substantially spherical.  
     
     
         13 . A magnetocaloric effect composite powder as defined in  claim 12 , wherein said core particles have a diameter of about 30 μm and said coating has a thickness between 50 nm and 200 nm.  
     
     
         14 . A magnetocaloric effect composite powder as defined in  claim 8 , wherein said coating is applied to said core particles using a chemical vapor deposition process.  
     
     
         15 . A method for enhancing the magnetocaloric effect within a giant magnetocaloric material comprising the step of coating a surface of said giant magnetocaloric material with an elastically stiff material, said elastically stiff material restricting volume changes of said giant magnetocaloric material during application of a magnetic field thereto.  
     
     
         16 . A method as defined in  claim 15 , wherein said giant magnetocaloric material is a compound of Gd 5 (Si 1-x  Ge x ) 4 .  
     
     
         17 . A method as defined in  claim 15 , wherein said elastically stiff coating is a low-coercivity, high-magnetization material.  
     
     
         18 . A method as defined in  claim 17 , wherein said coating of low-coercivity, high-magnetization material comprises an element selected from the group consisting of iron, cobalt, nickel, and magnetic oxides.  
     
     
         19 . A method as defined in  claim 15 , wherein said giant magnetocaloric material is coated on opposite surfaces.  
     
     
         20 . A method as defined in  claim 15 , wherein said giant magnetocaloric material is substantially encapsulated by said coating.  
     
     
         21 . A method of enhancing the magnetocaloric effect within a giant magnetocaloric material comprising the step of restricting volume changes of said giant magnetocaloric material during application of a magnetic field thereto.  
     
     
         22 . A method as defined in  claim 21 , wherein said volume changes of said giant magnetocaloric material is restricted by a coating of an elastically stiff material.  
     
     
         23 . A method as defined in  claim 22 , wherein said elastically stiff material is a low-coercivity, high-magnetization material.  
     
     
         24 . A method as defined in  claim 23 , wherein said low-coercivity, high-magnetization material comprises an element selected from the group consisting of iron, cobalt, nickel, and magnetic oxides.  
     
     
         25 . A method as defined in  claim 21 , wherein said giant magnetocaloric material is a compound of Gd 5 (Si 1-x  Ge x ) 4 .