A magnetic head includes a coil, a main pole, a write shield, a gap section, and a return path section. The main pole has a top surface including an inclined portion and a flat portion. The coil includes a specific coil element. The specific coil element has a front end portion, and an inclined surface contiguous with the front end portion. The write shield includes a top shield layer located on the front side in the direction of travel of a recording medium relative to the main pole, and located closer to a medium facing surface than the specific coil element. The top shield layer is located on the rear side in the direction of travel of the recording medium relative to an imaginary plane including the inclined surface of the specific coil element.

A magnetic head includes a main pole, a write shield and a gap section. The write shield includes a trailing shield, a leading shield and two side shields. The gap section includes a trailing gap section, a leading gap section and two side gap sections. Each of the two side gap sections and the leading gap section increases in thickness with increasing distance from a medium facing surface. In the medium facing surface, the thickness of the leading gap section is greater than the width of each of the two side gap sections, and the width of each of the two side gap sections decreases with decreasing distance to the leading gap section.

According to one embodiment, a magnetic disk device includes a magnetic recording medium, a head including a recording magnetic pole, a spin torque oscillator provided near the recording magnetic pole, and a coil which excites the recording magnetic pole, a first current supply which supplies the coil with a first current corresponding to write data, a detector which detects a first signal corresponding to the write data, and outputs a second signal in accordance with the first signal, and a second power supply which varies, in accordance with the second signal, a second current supplied to the spin torque oscillator.

A method for manufacturing a magnetic core module in a magnetic head, the magnetic core module and the magnetic head. The method for manufacturing the magnetic core module includes: a process for placing a magnetic core group in a holder mold cavity as an insert; and a process for injection-molding in the holder mold cavity. A method for manufacturing the magnetic core module allows the magnetic core group and the holder to be integrally injection-molded with a method of injection molding which uses the magnetic core group as an insert. The method simplifies the process of manufacturing a magnetic head to improve production efficiency, and saves labor and production costs. Further, the method prevents failures such as positional displacement and scattering of magnetic cores, which tends to occur when assembling thin and small magnetic cores, and ensures an ideal yield for a product.

A method for manufacturing a magnetic core module in a magnetic head, the magnetic core module and the magnetic head. The method for manufacturing the magnetic core module includes: a process for placing a magnetic core group in a holder mold cavity as an insert; and a process for injection-molding in the holder mold cavity. A method for manufacturing the magnetic core module allows the magnetic core group and the holder to be integrally injection-molded with a method of injection molding which uses the magnetic core group as an insert. The method simplifies the process of manufacturing a magnetic head to improve production efficiency, and saves labor and production costs. Further, the method prevents failures such as positional displacement and scattering of magnetic cores, which tends to occur when assembling thin and small magnetic cores, and ensures an ideal yield for a product.

A magnetic recording medium that can exhibit good traveling performance during use is provided. This magnetic recording medium is a tape-shaped magnetic recording medium, and includes a substrate including a polyester as a main component, a base layer disposed on the substrate, a magnetic layer disposed on the base layer, and a back layer disposed on a side of the substrate opposite to the base layer. A surface of the back layer opposite to the substrate has a kurtosis of 2.0 or more. On a surface of the magnetic layer, recesses having a depth of 20% or more of the average thickness of the magnetic layer are formed at a ratio of 10 or more and 200 or less per 1600 μm.sup.2. A surface of the magnetic layer has arithmetic average roughness Ra of 2.5 nm or less. The entire magnetic recording medium has a BET specific surface area of 3.5 m.sup.2/g or more in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried.

A magnetic recording medium that can exhibit good traveling performance during use is provided. This magnetic recording medium is a tape-shaped magnetic recording medium, and includes a substrate including a polyester as a main component, a base layer disposed on the substrate, a magnetic layer disposed on the base layer, and a back layer disposed on a side of the substrate opposite to the base layer. A surface of the back layer opposite to the substrate has a kurtosis of 2.0 or more. On a surface of the magnetic layer, recesses having a depth of 20% or more of the average thickness of the magnetic layer are formed at a ratio of 10 or more and 200 or less per 1600 μm.sup.2. A surface of the magnetic layer has arithmetic average roughness Ra of 2.5 nm or less. The entire magnetic recording medium has a BET specific surface area of 3.5 m.sup.2/g or more in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried.

A magnetic recording medium that can exhibit good traveling performance during use is provided. This magnetic recording medium is a tape-shaped magnetic recording medium, and includes a substrate, a base layer disposed on the substrate, and a magnetic layer disposed on the base layer. On the surface of the magnetic layer, recesses having a depth of 20% or more of the average thickness of the magnetic layer are formed at a ratio of 20 or more and 200 or less per 1600 μm.sup.2. On the surface of the magnetic layer, a logarithmic decay rate determined by a pendulum viscoelasticity test at a temperature of 10° C. or higher and 45° C. or lower is 0.025 or more and 0.040 or less. A difference between a maximum value of the logarithmic decay rate and a minimum value of the logarithmic decay rate is 0 or more and 0.020 or less. The squareness ratio in the perpendicular direction is 65% or more. The average thickness of the magnetic layer is 80 nm or less. The average thickness of the magnetic recording medium is 5.6 μm or less.

A magnetic recording medium that can exhibit good traveling performance during use is provided. This magnetic recording medium is a tape-shaped magnetic recording medium, and includes a substrate, a base layer disposed on the substrate, and a magnetic layer disposed on the base layer. On the surface of the magnetic layer, recesses having a depth of 20% or more of the average thickness of the magnetic layer are formed at a ratio of 20 or more and 200 or less per 1600 μm.sup.2. On the surface of the magnetic layer, a logarithmic decay rate determined by a pendulum viscoelasticity test at a temperature of 10° C. or higher and 45° C. or lower is 0.025 or more and 0.040 or less. A difference between a maximum value of the logarithmic decay rate and a minimum value of the logarithmic decay rate is 0 or more and 0.020 or less. The squareness ratio in the perpendicular direction is 65% or more. The average thickness of the magnetic layer is 80 nm or less. The average thickness of the magnetic recording medium is 5.6 μm or less.

A magnetic recording medium that can exhibit good traveling performance during use is provided. This magnetic recording medium is a tape-shaped magnetic recording medium, and includes a substrate, a base layer disposed on the substrate, and a magnetic layer disposed on the base layer. The substrate includes a polyester as a main component. The average thickness of the base layer is 0.9 μm or less. The base layer and the magnetic layer each include a lubricant. The magnetic layer has a surface having a large number of holes, and the arithmetic average roughness Ra of the surface is 2.5 nm or less. The BET specific surface area of the entire magnetic recording medium is 3.5 m.sup.2/g or more in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried. The squareness ratio in the perpendicular direction is 65% or more. The average thickness of the magnetic layer is 90 nm or less. The average thickness of the magnetic recording medium is 5.6 μm or less.