Patent ID: 11887634
Assignee: TOSHIBA ELECTRONIC DEVICES & STORAGE CORPORATION
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 0:
1. A magnetic disk device comprising:
a head structure comprising a reproducing head and a main magnetic pole gap installation portion behind a flying slider and including at least two thermal actuators; and
a control unit that can independently control the at least two thermal actuators, and that sets spacing of the reproducing head and the main magnetic pole gap installation portion with respect to a recording medium by setting a rotational speed at a time of contact, the rotational speed being a rotational speed of the recording medium, to be lower than a normal rotational speed when the reproducing head and the main magnetic pole gap installation portion are brought into contact with the recording medium, wherein
the control unit sets the spacing by using harmonic amplitude of a signal, the signal being previously recorded in the recording medium, at the rotational speed at the time of the contact of the reproducing head and the main magnetic pole gap installation portion, and
the control unit measures a spacing change amount Δd by using a following expression (1) on a basis of primary component amplitude V01 and tertiary component amplitude V03 in a contact state of a spacing measurement pattern, and primary component amplitude V11 and tertiary component amplitude V13 of a reproduction signal,, Δ
      ⁢
      d
     
     =
     
      
       λ
       
        4
        ⁢
        π
       
      
      ⁢
      
       (
       
        
         ln
         ⁢
         
          
           V
           11
          
          
           V
           13
          
         
        
        -
        
         ln
         ⁢
         
          
           V
           01
          
          
           V
           03
          
         
        
       
       )
      
     
    
   
   
    
     expression
     ⁢
        
     
      (
      1
      )
     
    
   
  
 

here, λ is a wavelength of a fundamental frequency.