Magnetic recording medium, producing method of the same magnetic recording system

Abstract

In a magnetic recording medium having Co-based alloy magnetic layer containing Pt formed on a substrate through an underlayer, by forming said underlayer with plural underlayers including double layer structure which is formed by piling up 1st underlayer of Cr-based alloy containing Ti and 2nd underlayer of Cr-based alloy containing at least one element selected from a group comprising Mo and W in this sequence, crystal grain diameter is decreased and then medium noise can be decreased, and c axis is oriented to in-plane direction and then high coercivity can be obtained, consequently the magnetic recording medium having high signal to noise ratio at high recording density region is obtained. Further a small size large capacity magnetic recording system can be provided by combination of said magnetic recording media with a MR (magnetoresistive) head.

What is claimed is:  
     
         1 . A magnetic recording medium having a Co-based alloy magnetic layer containing Pt formed on a substrate through a underlayer, characterized in that said underlayer comprises plural underlayers including double layers structure which is formed by piling up 1st underlayer of Cr-based alloy containing Ti, and 2nd underlayer of Cr-based alloy containing at least one element selected from a group comprising Mo and W, in this sequence.  
     
     
         2 . The magnetic recording medium as claimed in  claim 1 , wherein said 1st underlayer has body-centered cubic structure substantially.  
     
     
         3 . The magnetic recording medium as claimed in  claim 1 , wherein a fine crystalline metal layer or a substantially amorphous metal layer of which main component is Co or Ni, is formed between said substrate and 1st underlayer.  
     
     
         4 . The magnetic recording medium as claimed in  claim 1 , wherein an intermediate layer comprising an alloy of which main component are Co, Cr, and Pt, is formed between said 2nd underlayer and said magnetic layer.  
     
     
         5 . The magnetic recording medium as claimed in  claim 1 , wherein said magnetic layer comprises a Co-based alloy containing at least Cr, Pt, and Ta.  
     
     
         6 . The magnetic recording medium as claimed in  claim 5 , wherein Pt content in said magnetic layer is 3at. % or more and 25 at. % or less and Ta content in it is lat. % or more and Sat. % or less, Ti content in said 1st underlayer is Sat. % or more and 35 at. % or less, and the sum of Mo content and W content in said 2nd underlayer is Sat. % or more and 80 at. % or less.  
     
     
         7 . The magnetic recording medium as claimed in  claim 1 , wherein said magnetic layer comprises a Co-based alloy containing at least Cr, Pt, and B.  
     
     
         8 . The magnetic recording medium as claimed in  claim 7 , wherein Pt content in said magnetic layer is 3at. % or more and 25 at. % or less and B content in it is lat. % or more and 15 at. % or less, Ti content in said 1st underlayer is Sat. % or more and 35 at. % or less, and the sum of Mo content and W content in said 2nd underlayer is 5 at. % or more and 80 at. % or less.  
     
     
         9 . A producing method of a magnetic recording medium characterized in that the producing process includes a process to heat a substrate previous to forming 1st underlayer on the substrate, and a process to form a 1st underlayer, a 2nd underlayer, and a magnetic layer in this sequence in vacuum chambers by sequential sputtering method after heating the substrate, and that a target which comprises Cr-based alloy containing Ti is used to form said 1st underlayer, and a target which comprises Cr-based alloy containing at least one element selected from a group comprising Mo and W is used to form said 2nd underlayer.  
     
     
         10 . A producing method of a magnetic recording medium as claimed in  claim 9 , wherein said 1st underlayer has body-centered cubic structure substantially.  
     
     
         11 . A producing method of a magnetic recording medium as claimed in  claim 9 , wherein a fine crystalline metal layer or a substantially amorphous metal layer of which main component is Co or Ni, is formed between said substrate and 1st underlayer.  
     
     
         12 . A producing method of a magnetic recording medium as claimed in claim  9 , wherein an intermediate layer comprising an alloy of which main component are Co, Cr, and Pt, is formed between said 2nd underlayer and said magnetic layer.  
     
     
         13 . A producing method of a magnetic recording medium as claimed in  claim 9 , wherein said magnetic layer comprises a Co-based alloy containing at least Cr, Pt, and Ta.  
     
     
         14 . A producing method of a magnetic recording medium as claimed in  claim 13 , wherein Pt content in said magnetic layer is 3at. % or more and 25 at. % or less and Ta content in it is lat. % or more and Sat. % or less, Ti content in said 1st underlayer is 5at. % or more and 35 at. % or less, and the sum of Mo content and W content in said 2nd underlayer is 5at. % or more and 80 at. % or less.  
     
     
         15 . A producing method of a magnetic recording medium as claimed in  claim 9 , wherein said magnetic layer comprises a Co-based alloy containing at least Cr, Pt, and B.  
     
     
         16 . A producing method of a magnetic recording medium as claimed in  claim 15 , wherein Pt content in said magnetic layer is 3at. % or more and 25 at. % or less and B content in it is lat. % or more and 15 at. % or less, Ti content in said 1st underlayer is 5 at. % or more and 35 at. % or less, and the sum of Mo content and W content in said 2nd underlayer is 5at. % or more and 80 at. % or less.  
     
     
         17 . A magnetic recording system comprising a magnetic recording medium, a driving mechanism which drives said magnetic recording medium, a magnetic head which comprises a recording part and a reproducing part, an actuator which moves said magnetic head relatively to said magnetic recording medium, and a read and write signal processing means which sends recording signal to said head and processes reproduced signal from said head, which characterized in that a reproducing part of said magnetic head comprises a magnetoresistive sensor which includes plural conductive magnetic layers in which large resistance variation is occurred when mutual magnetization direction changes relatively by external magnetic field, and magnetoresistive sensor including conductive non-magnetic layers formed between said conductive magnetic layers, and said magnetic recording medium comprises the magnetic recording medium as claimed in  claim 1.