Magnetic recording medium having a dimensional variation
摘要
說明書
The above-mentioned squareness ratio S1 is determined as follows. First, a measurement sample is cut out from the elongated magnetic recording medium 10, and the M-H loop for the entire measurement sample, corresponding to the running direction (longitudinal direction) of the magnetic recording medium 10, is measured with the use of a VSM. Next, the coating film (the base layer 12, the recording layer 13, and the like) is wiped with the use of acetone, ethanol, or the like, thereby leaving only the substrate 11 for background correction, and with the use of a VSM, the M-H loop for the substrate 11 is measured which corresponds to the running direction of the substrate 11 (the running direction of the (magnetic recording medium 10). Thereafter, the M-H loop for the substrate 11 is subtracted from the M-H loop for the entire measurement sample to obtain an M-H loop after the background correction. The squareness ratio S1(%) is calculated by substituting the saturation magnetization Ms (emu) and remanent magnetization Mr (emu) of the obtained M-H loop into the following formula. Note that the M-H loops are all measured at 25° C. Squareness Ratio S1(%)=(Mr/Ms)×100 (Squareness Ratio S2 measured in Vertical Direction)
The squareness ratio S2 measured in the vertical direction (thickness direction) of the magnetic recording medium 10 is preferably 65% or more, more preferably 73% or more, and still more preferably 80% or more. When the squareness ratio S2 is 65% or more, the vertical orientation of the magnetic powder is sufficiently increased, thus allowing a better SNR to be achieved. Accordingly, better electromagnetic conversion characteristics can be obtained. Furthermore, the shape of the servo signal is improved, thereby making it easier to control the drive side.
