Magnetic powder, manufacturing method of magnetic powder, and magnetic recording medium
Magnetic powder includes: an epsilon-phase iron oxide-based compound selected from ε-Fe 2 O 3 or a compound represented by Formula (1). The magnetic powder has an average particle diameter of 8 nm to 25 nm, a ratio of Hc to Hc′ of from 0.6 to 1.0, and Hc′ satisfying Expression (II). Hc′ represents a magnetic field at which a value of Expression (I) becomes zero in a magnetic field-magnetization curve obtained by performing measurement at a maximum applied magnetic field of 359 kA/m, a temperature of 296 K, and a magnetic field sweeping speed of 1.994 kA/m/s. M represents magnetization and H represents applied magnetic field. Hc represents a magnetic field at which magnetization becomes zero in the magnetic field-magnetization curve. In Formula (1), A represents at least one metal element other than Fe, and a represents a number that satisfies a relationship of 0<a<2. d 2 M/dH 2 Expression (I) 119 kA/m< Hc ′<2380 kA/m Expression (II) ε-A a Fe 2-a O 3 (1)
1. Magnetic powder comprising:
at least one epsilon-phase iron oxide-based compound selected from the group consisting of ε-Fe 2 O 3 and a compound represented by Formula (1),
wherein the magnetic powder has an average particle diameter of 8 nm to 25 nm, a ratio of Hc to Hc′ is from 0.6 to 1.0, and Hc′ satisfies Expression (II),
wherein Hc′ represents a magnetic field at which a value of Expression (I) indicating a second derivative of magnetization M with respect to an applied magnetic field H becomes zero in a magnetic field-magnetization curve obtained by performing measurement at a maximum applied magnetic field of 359 kA/m, a temperature of 296 K, and a magnetic field sweeping speed of 1.994 kA/m/s, and Hc represents a magnetic field at which magnetization becomes zero in the magnetic field-magnetization curve;
d 2 M/dH 2 Expression (I)
119 kA/m< Hc′< 2380 kA/m Expression (II)
ε-A a Fe 2-a O 3 (1)
wherein, in Formula (1), A represents at least one metal element other than Fe, and a represents a number that satisfies a relationship of 0<a<2, and
wherein a content of magnetic powder having a particle diameter equal to or smaller than 7.5 nm with respect to a total content of magnetic powder is equal to or smaller than 5% by number.
2. The magnetic powder according to claim 1 ,
wherein the compound represented by Formula (1) is a compound represented by Formula (1-2),
ε-A 1 x A 2 y A 3 z Fe (2-x-y-z) O 3 (1-2)
wherein, in Formula (1-2), A 1 represents at least one trivalent metal element selected from the group consisting of Ga, Al, In, and Rh, A 2 represents at least one divalent metal element selected from the group consisting of Mn, Co, Ni, and Zn, A 3 represents at least one tetravalent metal element selected from the group consisting of Ti and Sn, x represents a number that satisfies a relationship of 0<x<1, y represents a number that satisfies a relationship of 0<y<1, z represents a number that satisfies a relationship of 0<z<1, and x+y+z<2.
3. The magnetic powder according to claim 1 ,
wherein a total content of at least one iron oxide-based compound selected from α-Fe 2 O 3 or γ-Fe 2 O 3 is equal to or smaller than 20 parts by mass with respect to 100 parts by mass of a total content of the at least one epsilon-phase iron oxide-based compound selected from the group consisting of ε-Fe 2 O 3 and the compound represented by Formula (1).
4. A magnetic recording medium comprising:
a non-magnetic support; and
a magnetic layer including the magnetic powder according to claim 1 and provided on the non-magnetic support.
5. Magnetic powder, comprising a compound represented by Formula (1),
wherein the magnetic powder has an average particle diameter of 8 nm to 25 nm, a ratio of Hc to Hc′ is from 0.6 to 1.0, and Hc′ satisfies Expression (II),
wherein Hc′ represents a magnetic field at which a value of Expression (I) indicating a second derivative of magnetization M with respect to an applied magnetic field H becomes zero in a magnetic field-magnetization curve obtained by performing measurement at a maximum applied magnetic field of 359 kA/m, a temperature of 296 K, and a magnetic field sweeping speed of 1.994 kA/m/s, and Hc represents a magnetic field at which magnetization becomes zero in the magnetic field-magnetization curve;
d 2 M/dH 2 Expression (1)
119 kA/m< Hc′< 2380 kA/m Expression (II)
ε-A a Fe 2-a O 3 (1)
wherein, in Formula (1), A represents at least one metal element other than Fe, and a represents a number that satisfies a relationship of 0<a<2, and
wherein a content of magnetic powder having a particle diameter equal to or smaller than 7.5 nm with respect to a total content of magnetic powder is equal to or smaller than 5% by number.
6. The magnetic powder according to claim 5 ,
wherein the compound represented by Formula (1) is a compound represented by Formula (1-2),
ε-A 1 x A 2 y A 3 z Fe (2-x-y-z) O 3 (1-2)
wherein, in Formula (1-2), A 1 represents at least one trivalent metal element selected from the group consisting of Ga, Al, In, and Rh, A 2 represents at least one divalent metal element selected from the group consisting of Mn, Co, Ni, and Zn, A 3 represents at least one tetravalent metal element selected from the group consisting of Ti and Sn, x represents a number that satisfies a relationship of 0<x<1, y represents a number that satisfies a relationship of 0<y<1, z represents a number that satisfies a relationship of 0<z<1, and x+y+z<2.
7. The magnetic powder according to claim 6 ,
wherein a total content of at least one iron oxide-based compound selected from α-Fe 2 O 3 or γ-Fe 2 O 3 is equal to or smaller than 20 parts by mass with respect to 100 parts by mass of a content of the compound represented by Formula (1).
8. A magnetic recording medium comprising:
a non-magnetic support; and
a magnetic layer including the magnetic powder according to claim 5 and provided on the non-magnetic support.