Tunneling magnetoresistance (TMR) device, its manufacture method, magnetic head and magnetic memory using TMR device

Abstract

A barrier layer is disposed over a pinned layer made of ferromagnetic material having a fixed magnetization direction, the barrier layer having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon. A first free layer is disposed over the barrier layer, the first free layer being made of amorphous or fine crystalline soft magnetic material which changes a magnetization direction under an external magnetic field. A second free layer is disposed over the first free layer, the second free layer being made of crystalline soft magnetic material which changes a magnetization direction under an external magnetic field and being exchange-coupled to the first free layer. A tunneling magnetoresistance device is provided which has good magnetic characteristics and can suppress a tunnel resistance change rate from being lowered.

1 . A tunneling magnetoresistance device comprising:
 a pinned layer made of ferromagnetic material having a fixed magnetization direction;   a barrier layer disposed over the pinned layer and having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon;   a first free layer disposed over the barrier layer and made of amorphous or fine crystalline soft magnetic material which changes a magnetization direction under an external magnetic field; and   a second free layer disposed over the first free layer and made of crystalline soft magnetic material which changes a magnetization direction under an external magnetic field and being exchange-coupled to the first free layer.   
     
     
         2 . The tunneling magnetoresistance device according to  claim 1 , wherein the first free layer is made of the soft magnetic material of CoFe added with at least one element selected from a group consisting of B, C, Al, Si and Zr. 
     
     
         3 . The tunneling magnetoresistance device according to  claim 1 , wherein the first free layer is made of CoFeB and a B concentration is 10 atom % or higher. 
     
     
         4 . The tunneling magnetoresistance device according to  claim 1 , wherein the second free layer is polycrystalline having a face centered cubic structure, and has non-orientation or has a (111) plane oriented preferentially in parallel to a substrate surface. 
     
     
         5 . The tunneling magnetoresistance device according to  claim 1 , wherein a coercive force of the second free layer is smaller than a coercive force of the first free layer. 
     
     
         6 . The tunneling magnetoresistance device according to  claim 1 , further comprising a crystallization suppressing layer disposed between the first and second free layers, the crystallization suppressing layer preventing the first free layer from being crystallized by inheriting a crystal structure of the second free layer. 
     
     
         7 . The tunneling magnetoresistance device according to  claim 6 , wherein the crystallization suppressing layer is made of Ta. 
     
     
         8 . A method for manufacturing a tunneling magnetoresistance device, comprising steps of:
 (a) forming a pinning layer made of antiferromagnetic material on a support substrate;   (b) forming a pinned layer over the pinning layer, the pinned layer being made of ferromagnetic material whose magnetization direction is fixed by an exchange interaction with the pinning layer;   (c) forming a barrier layer over the pinned layer, the barrier layer having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon;   (d) forming a first free layer made of amorphous or fine crystalline soft magnetic material over the barrier layer;   (e) exposing a surface of the first free layer to nitrogen plasma;   (f) forming a second free layer made of crystalline soft magnetic material over the first free layer exposed to the nitrogen plasma; and   (g) conducting a regularizing heat treatment process for the pinning layer by disposing a lamination structural body between the support substrate and the second free layer in a magnetic field.   
     
     
         9 . The method for manufacturing the tunneling magnetoresistance device according to  claim 8 , wherein the step (g) is performed under a condition that crystallization will not progress from an interface between the first and second free layers toward an inside of the first free layer. 
     
     
         10 . The method for manufacturing the tunneling magnetoresistance device according to  claim 8 , wherein the first free layer is made of the soft magnetic material of CoFe added with at least one element selected from a group consisting of B, C, Al, Si and Zr. 
     
     
         11 . The method for manufacturing the tunneling magnetoresistance device according to  claim 8 , wherein the first free layer is made of CoFeB and a B concentration is 10 atom % or higher. 
     
     
         12 . The method for manufacturing the tunneling magnetoresistance device according to  claim 8 , wherein the second free layer is polycrystalline having a face centered cubic structure, and has non-orientation or has a (111) plane oriented preferentially in parallel to a surface of the support substrate. 
     
     
         13 . The method for manufacturing the tunneling magnetoresistance device according to  claim 8 , wherein a coercive force of the second free layer is smaller than a coercive force of the first free layer. 
     
     
         14 . A method for manufacturing a tunneling magnetoresistance device, comprising steps of:
 (a) forming a pinning layer made of antiferromagnetic material on a support substrate;   (b) forming a pinned layer over the pinning layer, the pinned layer being made of ferromagnetic material whose magnetization direction is fixed by an exchange interaction with the pinning layer;   (c) forming a barrier layer over the pinned layer, the barrier layer having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon;   (d) forming a first free layer made of amorphous or fine crystalline soft magnetic material over the barrier layer;   (e) forming a crystallization suppressing layer over the first free layer;   (f) forming a second free layer made of crystalline soft magnetic material over the crystallization suppressing layer; and   (g) conducting a regularizing heat treatment process for the pinning layer by disposing a lamination structural body between the support substrate and the second free layer in a magnetic field,   wherein the crystallization suppressing layer suppressing the first free layer from being crystallized by inheriting a crystal structure of the second free layer during the step (g).   
     
     
         15 . The method for manufacturing the tunneling magnetoresistance device according to  claim 14 , wherein the first free layer is made of the soft magnetic material of CoFe added with at least one element selected from a group consisting of B, C, Al, Si and Zr. 
     
     
         16 . The method for manufacturing the tunneling magnetoresistance device according to  claim 14 , wherein the first free layer is made of CoFeB and a B concentration is 10 atom % or higher. 
     
     
         17 . The method for manufacturing the tunneling magnetoresistance device according to  claim 14 , wherein the second free layer is polycrystalline having a face centered cubic structure, and has non-orientation or has a (111) plane oriented preferentially in parallel to a substrate surface. 
     
     
         18 . The method for manufacturing the tunneling magnetoresistance device according to  claim 14 , wherein a coercive force of the second free layer is smaller than a coercive force of the first free layer. 
     
     
         19 . A magnetic head comprising:
 a pinned layer made of ferromagnetic material having a fixed magnetization direction;   a barrier layer disposed over the pinned layer and having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon;   a first free layer disposed over the barrier layer and made of amorphous or fine crystalline soft magnetic material which changes a magnetization direction under an external magnetic field; and   a second free layer disposed over the first free layer and made of crystalline soft magnetic material which changes a magnetization direction under an external magnetic field and being exchange-coupled to the first free layer.   
     
     
         20 . A magnetic memory comprising:
 a tunneling magnetoresistance device;   recording means for applying a magnetic field to the tunneling magnetoresistance device to change magnetization directions of first and second free layers of the tunneling magnetoresistance device; and   reproducing means for applying a sense current through the tunneling magnetoresistance device to detect a resistance of the tunneling magnetoresistance device,   wherein   the tunneling magnetoresistance device comprises:   a pinned layer made of ferromagnetic material having a fixed magnetization direction;   a barrier layer disposed over the pinned layer and having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon;   the first free layer disposed over the barrier layer and made of amorphous or fine crystalline soft magnetic material which changes a magnetization direction under an external magnetic field; and   the second free layer disposed over the first free layer and made of crystalline soft magnetic material which changes a magnetization direction under an external magnetic field and being exchange-coupled to the first free layer.