hereinafter , embodiments of the present invention will be described with reference to the drawings . fig1 ( a ) and 1 ( b ) are conceptual diagrams showing a disk drive according to an embodiment of the present invention . fig1 ( a ) is a top view of the disk drive , and fig1 ( b ) is a side view of the disk drive . a magnetic head mounted on a slider 13 fixed to the tip of a suspension arm 12 writes and reads magnetized signals at a predetermined position on a magnetic disk rotated by a motor 4 . it is possible to select a position ( track ) of the magnetic head on the magnetic disk in a radial direction of the magnetic disk by driving a rotary actuator 15 . a write signal to the magnetic head and a read signal from the magnetic head are processed by signal processing circuits 35 a and 35 b . fig2 shows an external view of a head suspension assembly of the present invention . the head suspension assembly has a suspension arm 12 , the slider 13 fixed to the tip of the suspension arm 12 , and a read element formed on a trailing edge side of the slider . fig3 is a diagram showing a magnetic head of the longitudinal magnetic recording method as viewed from a sectional direction of a magnetic disk . a read head has a read element 25 disposed on a substrate 34 and sandwiched between an upper magnetic shield 29 and a lower magnetic shield 27 . a current is applied to the read element 25 by an electrode . a write head defines a magnetic gap on an air bearing surface facing a magnetic disk 33 by way of a lower pole 30 , an upper pole 31 , and a magnetic gap layer 32 positioned between the upper and lower poles 31 , 32 . with the longitudinal recording method , a magnetic flux leaked from the lower pole 30 magnetizes an orbital track on the magnetic medium in the longitudinal direction as shown in fig3 in a writing operation . the read element 25 of the read head injects the magnetic flux into the magnetized region on the rotating magnetic medium to cause a change in resistance inside the read element 25 in a reading operation . shown in fig4 is a diagram illustrating a magnetic head of the vertical magnetic recording method as viewed from a sectional direction of a magnetic disk . a read head has a read element 25 disposed on a substrate 34 and sandwiched between an upper magnetic shield 29 and a lower magnetic shield 27 . a current is applied to the read element 25 by an electrode . a write head defines a magnetic gap on an air bearing surface facing to the magnetic disk 33 by way of a lower pole 30 , an upper pole 31 , and a magnetic gap layer 32 positioned between the upper and lower poles 31 , 32 . in a writing operation , a signal current is guided through a coil layer c , and a magnetic flux leaks onto the air bearing surface . the leaked magnetic flux returns to the magnetic head via a lower soft magnetic film 34 of the recording medium . the magnetic flux magnetizes an orbital track on the magnetic medium in the vertical direction . in a reading operation , the read element 25 of the read head injects the magnetic flux into the magnetized region on the rotating magnetic medium to cause a change in resistance inside the read element 25 , which is detected as a change in voltage of the read element 25 . shown in fig5 is a relationship between the time it takes for a charge charged on the read element to diffuse and a resistance value between the read element and the slider . as is apparent from fig5 , the diffusion time is determined depending on the resistance value . the resistance value between the read element and the slider is a value determined by a resistance value rr between the electrode and the shield , a resistance value r 1 between the shield and the slider , and the resistance value rc of the protection film on the air bearing surface . when a diffusion constant is small , a large current flows to the read element to damage the read element . in turn , when a diffusion constant is large , the charge is retained for a long period of time to cause static electricity destruction during assembling . therefore , the resistance between the electrode of the read element and the slider may preferably be in the range of about 10 6 ω to 10 11 ω . fig6 shows a method for measuring the resistance value of fig5 . a resistance value between a read element terminal 37 and the slider 13 is measured by a high resistance meter . fig7 shows a method for measuring the diffusion time in fig5 . a surface of the slider 13 is grounded to be charged by a power unit 16 ( through a wire 22 , a plate 21 , and a contact probe 18 ) via a lead terminal 17 of the suspension 12 , and then a damping time is measured by a potential meter 20 and displayed on a digital oscilloscope 19 . fig1 shows a magnetic head according to a first embodiment of the present invention . in this embodiment , a 1 nm - thick si underlayer is formed and then a 2 nm - thick cac carbon film is formed on the si underlayer to obtain an abs protection film 38 . further , a 0 . 7 nm - thick base alumina is formed , and a 3 - μm thick lower magnetic shield 27 is formed . with the above constitution , a resistance value between a slider 13 and a read element terminal 37 becomes 10 10 ω , wherein a diffusion time becomes 10 ms . fig1 shows a magnetic head according to a second embodiment of the present invention . in this embodiment , a dense film is formed under decreased gas pressure by changing a sputtering rate for a cac carbon from 10 − 4 torr to 10 − 5 torr . a 1 nm - thick si underlayer is formed and then a 2 nm - thick cac carbon film is formed on the si underlayer to obtain an abs protection film 38 . further , a 0 . 7 nm - thick base alumina is formed , and a 3 μm - thick lower magnetic shield 27 is formed . with the above constitution , a resistance value between a slider 13 and a read element terminal 37 becomes 10 8 ω , wherein a diffusion time becomes 1 ms . fig8 is a diagram showing a relationship between the base alumina film thickness and the resistance value . as is apparent from fig8 , it is possible to reduce the resistance value when the base alumina 39 of the magnetic heads shown in fig1 and 13 is decreased in thickness . fig9 is a diagram showing a relationship between the protection film thickness and the resistance value . as is apparent from fig9 , it is possible to reduce the resistance value when the protection film 32 of the magnetic heads shown in fig1 and 13 is decreased in thickness . fig1 shows a dependency on the method for forming the protection film . as is apparent from fig1 , the cac carbon used in the present invention reduces the resistance value relative to a conventional cvd carbon . fig1 is a diagram showing a relationship between protection film processing and the resistance value . as is apparent from fig1 , the resistance value is reduced by using about 10 % of nitride in the cac carbon method as in the second embodiment . it is to be understood that the above description is intended to be illustrative and not restrictive . many embodiments will be apparent to those of skill in the art upon reviewing the above description . the scope of the invention should , therefore , be determined not with reference to the above description , but instead should be determined with reference to the appended claims along with their full scope of equivalents .