Magnetoresistive element with oxide magnetic layers and metal magnetic films deposited thereon

Abstract

No related magnetoresistive multi-layered films made from a metal magnetic film provide sufficient reproducing output power. A high-polarized layer with a thickness of 10 nm or less is formed as a Fe-rich Fe—O layer in contact with the interface of a non-magnetic intermediate layer and the resulting layers are heat treated to form a multi-layered film of ferromagnetic Fe—O layers, achieving a magnetoresistive element having high magnetoresistance.

What is claimed is:  
     
         1 . A magnetoresistive element having a multi-layered composition of a ferromagnetic layer/a non-magnetic intermediate layer/a ferromagnetic layer, which are separated through the non-magnetic intermediate layer and has at least two ferromagnetic layers, and including elements, which allows the multi-layered composition to induce magnetoresistance when a relative magnetization angle defined between the ferromagnetic layers varies depending on an external magnetic field exerted, and at least one pair of electrodes for detecting the change in said magnetoresistance, wherein: 
 at least one of said ferromagnetic layers is comprised of a high-polarized layer; and    at least one of the non-magnetic intermediate layer-ferromagnetic layer interface has a composition of a non-magnetic intermediate layer/a high-polarized layer/a ferromagnetic metal layer, said high-polarized layer being a ferromagnetic compound such as half-metal or a mixture of any of ferromagnetic compounds and metal.    
     
     
         2 . The magnetoresistive element claimed in  claim 1 , wherein: 
 at least one of said ferromagnetic layers is composed of a multi-layered construction of the high-polarized layer and the ferromagnetic metal layer; and    at least one of the non-magnetic intermediate layer-a ferromagnetic layer interface has the composition of the non-magnetic intermediate layer/the high-polarized layer/the ferromagnetic metal layer, said high-polarized layer being a ferromagnetic compound such as half-metal or a mixture of any of ferromagnetic compounds and metal.    
     
     
         3 . The magnetoresistive element claimed in  claim 1 , wherein: 
 at least one of said ferromagnetic layer is composed of a multi-layered construction containing the ferromagnetic compound or the multi-layered construction of the high-polarized layer and the ferromagnetic metal layer containing the ferromagnetic compound, and    at least one of the non-magnetic intermediate layer-ferromagnetic layer interface has the composition of the non-magnetic intermediate layer/the high-polarized layer/the ferromagnetic metal layer, said high-polarized layer being a ferromagnetic oxide mainly composed of magnetite, Fe 3 O 4-x  (x is 0-3, and preferably 2-3), or MFe 2 O 4-x  (M═Fe, Co, Ni, Mn, Cr, or Zn, x is 0-3, and preferably 2-3), a mixture of said ferromagnetic oxide and Fe, or a mixture of said ferromagnetic oxide and the ferromagnetic metal including any of Fe, Co, Ni, and the like.    
     
     
         4 . The magnetoresistive element claimed in  claim 1 , wherein: 
 a magnetization orientation of one of ferromagnetic layers with the composition of said ferromagnetic layer/non-magnetic intermediate layer/ferromagnetic layer is fixed substantially to the magnetic field to be sensed by means of the antiferromagnetic film and a fixing means, such as exchange coupling deposited on its whole surface.    
     
     
         5 . A magnetoresistive element having the multi-layered composition of a first ferromagnetic metal layer/a non-magnetic intermediate layer/a second ferromagnetic layer/a antiparallel coupling layer/a third ferromagnetic metal layer/a antiferromagnetic film, and including the elements, which allows the said multi-layered composition to induce magnetoresistance when a relative magnetization angle defined between said first ferromagnetic layers varies depending on an external magnetic field exerted, and at least one pair of electrodes for detecting the change in said magnetoresistance, wherein: 
 the magnetization of said third ferromagnetic layer is fixed substantially to the magnetic field to be sensed by means of said antiferromagnetic film and exchange coupling deposited on its whole surface by means of an exchange coupling force applied by said antiferromagnetic film, by which the magnetization of said second ferromagnetic layer is fixed substantially antiparallel to the magnetization orientation of said third ferromagnetic layer by means of the exchange coupling force applied by said antiparallel coupling layer, further by which the magnetization of said second ferromagnetic metal layer is fixed substantially to the magnetic field to be sensed, and    said second ferromagnetic layer is composed of the multi-layered construction of the high-polarized layer, which is a mixture of the ferromagnetic oxide or the ferromagnetic oxide with a high-polarization and the ferromagnetic metal, and of the ferromagnetic metal layer;    said magnetoresistive element having the composition of the first ferromagnetic layer/the non-magnetic intermediate layer/the high-polarized layer/the ferromagnetic metal layer.    
     
     
         6 . The magnetoresistive element claimed in  claim 5 , wherein: 
 each of said first and second ferromagnetic layers is composed of the multi-layered construction of the high-polarized layer, which is a mixture of the ferromagnetic oxide or the ferromagnetic oxide with a high-polarization and the ferromagnetic metal, and of the ferromagnetic metal layer;    said magnetoresistive element having the composition of the first ferromagnetic metal layer/the non-magnetic intermediate layer/the second high-polarized layer/the second ferromagnetic metal layer.    
     
     
         7 . The magnetoresistive element claimed in  claim 1 , wherein said high-polarized layer has a thickness of 0.5-5 nm, and preferably 1-3 nm.  
     
     
         8 . The magnetoresistive element claimed in  claim 1 , wherein said non-magnetic intermediate layer is composed of any conductive metals such as Cu or Au, Ag, Al, Pt, Pd, Os, Re, Ru, and Rh.  
     
     
         9 . The magnetoresistive element claimed in  claim 1 , wherein said non-magnetic intermediate layer is composed of an insulating film made from any of materials such as alumina and said magnetoresistance is the tunnel effect.  
     
     
         10 . The magnetoresistive element claimed in  claim 1 , wherein said ferromagnetic layer contains an oxide inserting layer having the function of an electron reflection layer, diffusion control layer, or crystallinity improvement layer and have the composition of the ferromagnetic metal layer/the oxide inserting layer/the ferromagnetic metal layer.  
     
     
         11 . The magnetoresistive element claimed in  claim 1 , wherein said electrodes are structured so that they apply current parallel to the multi-layered surface of said multi-layered composition.  
     
     
         12 . The magnetoresistive element claimed in  claim 1 , wherein said electrodes are structured so that they apply current in the direction of thickness of the film in said multi-layered composition.