Patent ID: 11887634
Assignee: KABUSHIKI KAISHA TOSHIBA
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 4:
5. A control method of a magnetic disk device that includes 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, the control method comprising:
setting, when bringing the reproducing head and the main magnetic pole gap installation portion into contact with a recording medium, 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 in a state of being capable of independently controlling the at least two thermal actuators; and
setting spacing of the reproducing head and the main magnetic pole gap installation portion with respect to the recording medium at the rotational speed at the time of the contact, wherein
setting of the spacing is performed by utilization of 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
in setting of the spacing, a spacing change amount Δd is measured by utilization of 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
           
            1
            ⁢
            1
           
          
          
           V
           
            1
            ⁢
            3
           
          
         
        
        -
        
         ln
         ⁢
         
          
           V
           
            0
            ⁢
            1
           
          
          
           V
           
            0
            ⁢
            3
           
          
         
        
       
       )
      
     
    
   
   
    
     expression
     ⁢
        
     
      (
      1
      )
     
    
   
  
 

here, λ is a wavelength of a fundamental frequency.