Magnetic recording medium and magnetic storage apparatus

A magnetic recording medium comprising:

• a nonmagnetic substrate;
• an underlayer including at least one NaCl type compound that is MgO, TiO or NiO and disposed above the nonmagnetic substrate;
• and
• a magnetic recording layer disposed on the underlayer, wherein
• the magnetic recording layer includes a first magnetic layer disposed on and in contact with the underlayer, and a second magnetic layer disposed above the first magnetic layer,
• each of the first magnetic layer and the second magnetic layer has a granular structure including magnetic grains having a L10 structure and a grain boundary portion,
• the grain boundary portion of the first magnetic layer includes aluminum nitride,
• the grain boundary portion of the second magnetic layer includes hexagonal boron nitride,
• an absolute value of a Gibbs free energy of oxidation reaction for aluminum included in the grain boundary portion of the first magnetic layer is larger than that for an element, other than aluminum, included in the first magnetic layer and the second magnetic layer,
• the second magnetic layer has an intergrain distance that is less than 8.0 nm,
• an aluminum nitride content in the first magnetic layer is in a range of 15 vol % to 35 vol %,
• a peak in a B1s spectrum of the grain boundary portion of the second magnetic layer observed using X-ray photoelectron spectroscopy is 191.6 eV or less,
• the magnetic recording medium has a saturation magnetization that is 688.7 emu/cm3 or more, and
• the element included in the first magnetic layer and the second magnetic layer is B, Fe or Pt, such that the aluminum included in the grain boundary portion of the first magnetic layer is more easily oxidized than the element included in the first magnetic layer and the second magnetic layer and the aluminum reacts with oxygen that diffuses from the nonmagnetic substrate or the underlayer to prevent the oxygen from diffusing into the second magnetic layer.