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US4770933A Expired / Lapsed US ⏱️ 0.0 years remaining

Magnetic recording medium

Assignee: Maxell Ltd
•
Filing: 1988-01-11
•
Granted: 1988-09-13
•
Expires: 2008-01-11
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Abstract

Abstract A magnetic recording medium which comprises a substrate and a magnetic layer comprising hexagonal system ferrite powder of the formula: AOxn{[Fe1-(x+y)xM2+xxM4+y]2O3}(I) wherein, A is at least one metal selected from the group consisting of Ba, Sr, Pb and Ca, M2+ is at least one divalent metal ion selected from the group consisting of Mn, Co, Ni, Cu, Zn and Mg, M4+ is at least one tetravalent metal ion selected from the group consisting of Ti, Zr, Sn, Ge, V and Nb, n is a number of 3 to 8, x and y are such numbers that x+y is from 0.02 to 0.3 and x/y is from 0.2 to 0.8., and which has a temperature dependency such that the coercive force of the magnetic layer is at a minimum in the temperature range of -20 DEG to 50 DEG C. and has a higher coercive force outside said temperature range has good storage property.

Inventors

  • 👤 Shinichi Kitahata
  • 👤 Mikio Kishimoto

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-30 10:41
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/25; Y10T428/29; Y10T428/2982

Claims Analysis

Total Claims: 3
Claim 1
Independent Claim 156 words
A magnetic recording medium which comprises a substrate and a magnetic layer comprising hexagonal system ferrite powder of the formula: AO·n{[Fe.sub.1-(x+y) ·M.sup.2+.sub.x ·M.sup.4+.sub.y ].sub.2 O.sub.3 } (I) wherein, A is at least one metal selected from the group consisting of Ba, Sr, Pb and Ca, M 2+ is at least one divalent metal ion selected from the group consisting of Mn, Co, Ni, Cu, Zn and Mg, M 4+ is at least one tetravalent metal ion selected from the group consisting of Ti, Zr, Sn, Ge, V and Nb, n is a number of 3 to 8, x and y are such numbers that x+y is from 0.02 to 0.3 and x/y is from 0.2 to 0.8., and which has a temperature dependency such that the coercive force of the magnetic layer is at a minimum in the temperature range of -20° to 50° C. and has a higher coercive force outside of said temperature range.
Claim 2
Dependent Claim 156 words
A magnetic recording medium which comprises a substrate and a magnetic layer comprising hexagonal system ferrite powder of the formula: AO·n{[Fe.sub.1-(x+y) ·M.sup.2+.sub.x ·M.sup.4+.sub.y ].sub.2 O.sub.3 } (I) wherein, A is at least one metal selected from the group consisting of Ba, Sr, Pb and Ca, M 2+ is at least one divalent metal ion selected from the group consisting of Mn, Co, Ni, Cu, Zn and Mg, M 4+ is at least one tetravalent metal ion selected from the group consisting of Ti, Zr, Sn, Ge, V and Nb, n is a number of 3 to 8, x and y are such numbers that x+y is from 0.02 to 0.3 and x/y is from 0.2 to 0.8., and which has a temperature dependency such that the coercive force of the magnetic layer is at a minimum in the temperature range of -20° to 50° C. and has a higher coercive force outside of said temperature range.
Claim 3
Dependent Claim 32 words
The magnetic recording medium according to claim 1, wherein the ratio x/y is from 0.3 to 0.6 and the coercive force is minimum in the temperature range of -10° to 30° C.

References Cited (Backward Citations)

US4425250A Cited
US4511617A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1991-09-13 1992-03-14 1992-09-13 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1995-09-13 1996-03-14 1996-09-13 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1999-09-13 2000-03-14 2000-09-13 $7700.00 Window Closed / Lapsed

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