Exchange-coupled film, method for making exchange-coupled film, and magnetic sensing element including exchange-coupled film

Abstract

An exchange-coupled film includes a seed layer, an antiferromagnetic layer, and a ferromagnetic layer. The seed layer is formed at a thickness that is larger than the critical thickness, and the thickness of the seed layer is then decreased by etching so as to be smaller than or equal to the critical thickness. Thereby, a crystalline phase which extends through the seed layer from the upper surface to the lower surface can be formed, and/or the average size, in a direction parallel to the layer surface, of the crystal grains in the seed layer can be set to be larger than the thickness of the seed layer. Consequently, a large exchange coupling magnetic field Hex can be generated between the antiferromagnetic layer and the ferromagnetic layer.

1 - 16 . (canceled)  
     
     
         17 . A method for making an exchange-coupled film comprising the steps of: 
 (a) forming a seed layer at a thickness that is larger than a critical thickness so that a crystalline phase extends through from a upper surface to a lower surface of the seed layer;    (b) etching the upper surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness; and    (c) depositing an antiferromagnetic layer and a ferromagnetic layer on the seed layer.    
     
     
         18 . A method for making an exchange-coupled film comprising the steps of: 
 (d) forming a seed layer with a crystalline phase at a thickness that is larger than a critical thickness;    (e) etching a surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness and so that an average size, in a direction parallel to the layer surface, of the crystal grains in the seed layer is larger than the thickness of the seed layer; and    (f) depositing an antiferromagnetic layer and a ferromagnetic layer on the seed layer.    
     
     
         19 . The method for making the exchange-coupled film according to  claim 17 , wherein in said step (a), the seed layer is formed with a metal material which has a face-centered cubic structure and a crystalline phase in which the equivalent crystal plane represented as {111} plane is preferentially oriented parallel to an interface between the antiferromagnetic layer and the ferromagnetic layer.  
     
     
         20 . The method for making the exchange-coupled film according to  claim 17 , wherein the seed layer is formed with a NiCr alloy or a NiFeCr alloy.  
     
     
         21 . A method for making an exchange-coupled film comprising the steps of: 
 (g) forming a seed layer at a thickness that is larger than a critical thickness with a NiCr alloy or a NiFeCr alloy having a Cr content of 35 to 60 atomic percent;    (h) etching a surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness; and    (i) depositing an antiferromagnetic layer and a ferromagnetic layer on the seed layer.    
     
     
         22 . The method for making the exchange-coupled film according to  claim 20 , wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 40 to 60 atomic percent, and in said step (b), the seed layer is etched so that the thickness of the seed layer is larger than 0 Å and smaller than or equal to 38 Å.  
     
     
         23 . The method for making the exchange-coupled film according to  claim 20 , wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 35 to 60 atomic percent, and in said step (b), the seed layer is etched so that the thickness of the seed layer is larger than 0 Å and smaller than or equal to 30 Å.  
     
     
         24 . The method for making the exchange-coupled film according to  claim 21 , wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 50 atomic percent or less.  
     
     
         25 . The method for making the exchange-coupled film according to  claim 22 , wherein in the NiFeCr alloy, the Fe/Ni atomic ratio is greater than 0/100 and less than or equal to 30/70.  
     
     
         26 . The method for making the exchange-coupled film according to  claim 22 , wherein in said step (b), the thickness of the seed layer is set at 6 Å or more.  
     
     
         27 . The method for making the exchange-coupled film according to  claim 26 , wherein in said step (b), the thickness of the seed layer is set at 12 Å or more.  
     
     
         28 . A method for making an exchange-coupled film comprising the steps of: 
 (a) forming a seed layer at a thickness that is larger than a critical thickness so that a crystalline phase extends through from an upper surface to a lower surface of the seed layer;    (b) etching the upper surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness; and    (j) depositing a ferromagnetic layer on the seed layer.