JPH0927101A - Magnetic memory method and magnetic memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high-density and high-frequency recording without changing a recording head material and specifically reducing the distance between a magnetic head and a magnetic recording medium and without deteriorating the overwriting characteristic of the magnetic recording medium, the magnetic head and a recording and reproducing amplifier. SOLUTION: The design of a magnetic memory device is executed in such a manner that the various parameters determined by the magnetic head, the magnetic recording medium, recording amplifier, etc., satisfy the following equation 1, equation 2 or equation 3: v×(tr +tf )/2<=L (1) v×(tr +tf )<=2π×Br×tmag / Hc (2) fw <=1/(tr +tf ) (3). In the equations, (v) is the relative speed (m/sec) between the head and the medium; tr is the rising time (sec) of the recording current, tf is the falling (sec) of the recording current; L is the magnetization inversion width on the medium; Br is the residual magnetic flux density (Gauss) of the magnetic recording medium; tmag is the magnetic film thickness (m) of the magnetic recording medium; Hc is the coercive force (Oe) of the magnetic recording medium; fw is a recording and reproducing frequency (Hz).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a magnetic disk device and a V disk.
Regarding a magnetic storage device such as a TR, it has a recording density of 2 gigabits or more per square inch, and sufficiently secures overwrite characteristics during high frequency recording without particularly reducing the distance between the magnetic head and the magnetic recording medium. The present invention relates to a magnetic storage device capable of improving reproduction resolution and, as a result, achieving high density and high frequency recording.

[0002]

2. Description of the Related Art To perform saturated magnetic recording in a magnetic storage device, it is important to improve overwrite characteristics (hereinafter abbreviated as OW characteristics). The OW characteristic is measured by the following method.
First, data is recorded at a specific frequency (hereinafter referred to as 1F frequency), and the signal power N ′ of the fundamental wave component is measured. Next different frequency (hereinafter referred to as 2F frequency)
The data is overwritten with and the power of the remaining signal at the 1F frequency is measured as N. The OW characteristic is defined by the signal powers N and N ′ as in the following equation.

OW (N ′ / N) [dB] ≡20Log (N ′ / N) Conventionally, the OW characteristic of a thin film magnetic recording medium is determined by the magnetic field generated by the recording head and the internal magnetic field generated by the magnetization distribution inside the medium. It has been said that it will be done (for example, Ito, Tagawa,
Nakamura: IEICE Transactions C-II, Vol.J75-C-II, N
o.12, p.762, 1992). This model has made it possible to analyze the OW characteristics fairly quantitatively.

[0004]

By the way, in recent years, the demand for higher recording density of magnetic storage devices has been increasing. In order to improve the linear recording density, it is necessary to increase the coercive force of the medium, and in order to secure sufficient OW characteristics, it is necessary to change the head structure and material and increase the magnetomotive force. To increase the magnetomotive force, it is necessary to increase the recording current value (hereinafter abbreviated as I _w ) or increase the number of turns of the recording head. The setting of the I _w are related largely to design a recording amplifier, where the upper limit of I _w is determined. In designing a self-recording / reproducing inductive magnetic head, it is necessary to increase the number of coil windings of the head in order to secure a reproduction output value.
In the case of a recording / reproducing separated type magnetic head, the number of turns of the recording head may be determined from the recording current value allowed by the recording / reproducing circuit (IC) and the required magnetomotive force.

In addition to high recording density, high frequency recording is strongly desired for high speed transfer. This includes I
_w rise and fall time of the (each t _r, abbreviated as t _f) the need to reduce, and to reduce the inductance of the recording head in the sense to reduce the load connected to the recording amplifier, current switching characteristics of the recording amplifier itself It is necessary to speed up. When the number of coil windings of the head is decreased to reduce the inductance of the recording head, the magnetomotive force decreases. Therefore, in order to ensure sufficient OW characteristics, a high saturation magnetic flux density material such as CoNiFe or FeN is used for the recording head magnetic pole. It is necessary to adopt it or reduce the flying height of the head. Conventionally, in consideration of the medium as well as the head and the recording amplifier only, t _r, examples were quantitatively examined the relationship between t _f and the OW characteristic was not. Therefore, when designing the magnetic storage device, ensure sufficient OW characteristics in the high frequency region,
The conditions required for the recording / reproducing system to obtain the recording / reproducing characteristics with a good S / N ratio were not clear.

Against this background, the present invention relates to a magnetic recording medium, a magnetic head and a recording / reproducing amplifier used in a magnetic storage device such as a magnetic disk device or a VTR.
An object of the present invention is to provide a method for achieving high-density and high-frequency recording without changing the recording head material or reducing the distance between the magnetic head and the magnetic recording medium, without deteriorating the OW characteristics. .

[0007]

In order to achieve the above object, the present invention relates to various parameters determined by a magnetic head, a magnetic recording medium, a recording / reproducing IC, etc., by the following expressions (1) and (2). The magnetic storage device is designed so as to satisfy the expression (3). _{v × (t r + t f} ) / 2 ≦ L (1) v × (t r + t f) / 2 ≦ 5 × Br × t mag / Hc (2) f w ≦ 1 / (t r + t f) (3 ) However, v: between the head medium relative velocity (m / sec) t _r: the recording current rise time (sec) t _f: recording current fall time (sec) Br: residual magnetic flux density of the magnetic recording medium (Gauss) t _mag : magnetic thickness of the magnetic recording medium (m) Hc: magnetic recording medium coercivity (Oe) f _w: where recording frequency (Hz), the recording current rise time t _r when the recording current is switched while increasing It is the time between 10% and 90% of the recording current reversal amount, which is the recording current fall time t.
_f is the time taken to cross 10% and 90% of the recording current reversal amount when switching while the recording current is decreasing.

[0008]

By designing the device so as to satisfy the above condition (1), (2) or (3), the material of the recording head is changed or the distance between the magnetic head and the magnetic recording medium is particularly reduced. It is possible to achieve high-density, high-frequency recording without degrading the OW characteristics. The reason is shown below.

The magnetization transition width Lo at the time of recording under ideal conditions is the Williams-Comstock model (ML
Willaims et al., AIP Conf. Proc., 5, 7387, 19
According to 72), it is described by the parameter πa (Lo≈πa). Where a is M _{r the} medium residual magnetization,
Hc the media coercivity, S ^* medium squareness ratio, g _l a recording head gap length, the head medium between the spacing of h _m, a magnetic medium film thickness t, is expressed by the following equation.

A = a₁/ 2r + [(a₁/ 2r)^Two+ 2πχ
ta₁/ R]^1/2 a₁/ 2r = y (1-S^*) / ΠQ + [{y (1-S^*)
/ ΠQ}^Two+ (2M_rt / Hc) (2y / Qr)]^1/2 y = [h_m(H_m+ T)]^1/2 Q = 0.866-0.216exp (-5y / 3g_l) r = 1-χ (1-S^*) Hc / M_r χ = M_r/ 4Hc Recording current waveform 1 is switching as shown in FIG.
Magnetization transition length of Williams-Comstock with characteristics
Recording current reversal distance (t _rXv)
Or (t_fWhen xv) is small, it is shown in Fig. 1 (b).
As described above, the magnetization transition actually formed on the magnetic recording medium 2
The width L of the transfer region 4 becomes substantially equal to Lo. In Fig. 1 (b)
The arrow 3 indicates the direction of recording magnetization. However, conversely to πa
The recording current reversal distance (t_r× v) or (t_f×
When v) is large, as shown in FIGS. 2 (a) and 2 (b)
And the width of the magnetization transition region 4 formed on the magnetic recording medium 2.
L is (t _r× v) or (t_fXv) is almost equal to
You. The magnetization transition part corresponds to the recording current reversal part,
Recording magnetic field does not occur. Therefore, the magnetization transition width is large.
Becomes difficult to secure sufficient OW characteristics.
it is conceivable that.

In order to actually confirm the above model, FIG.
As shown in, the inductance L7 is connected in series with the recording head 5.
Adding, to evaluate the OW characteristic by changing t _r, t _f by varying the value of L. In the figure, 6 is a recording amplifier. The conditions for the OW characteristic evaluation experiment are shown below. High density signal 88kFC on top of low density signal 15.6kFCI
I was recorded, and the overwrite erasing ratio of the 15.6 kFCI signal, that is, the ratio of the 15.6 kFCI signal intensity before overwriting and the 15.6 kFCI signal component intensity that remained after overwriting was evaluated. Relative velocity between head media v
Was set to 25.6 m / s and the flying height of the head was set to 50 nm to evaluate the OW characteristics. _{(Br × t ma g / Hc} ) values of the medium are 36～50Nm,? Pa value 160~240n
m.

OW (N '/ N) recording current reversal distance [(t _r
+ T _f ) × v / 2] dependence measurement result is shown in FIG. FIG.
Therefore, the recording current reversal distance [(t _r + t _f ) × v / 2] is 2
[(T _r + t _f ) × v /
2], there is no change in OW (N ′ / N), but in the larger region of [(t _r + t _f ) × v / 2] beyond that, [(t _r
+ T _f ) × v / 2] increases, and OW (N ′ / N) decreases. OW (N '/ in a sufficiently small recording current reversal area
The recording current reversal distance at which OW (N ′ / N) decreases by 3 dB with respect to the (N) value is defined as “OW3 dB decrease length”. FIG. 5 shows that the OW 3 dB reduction length is 4 between 160 and 20 nm.
It is plotted for various types of media of πa. From FIG. 5, it can be seen that the OW3 dB reduction length is approximately 1.2πa. That is, when the recording current reversal distance becomes about πa, the OW characteristic starts to deteriorate. This shows the validity of this model.

Meanwhile, in the simple model, the magnetic transition width of the medium is proportional to the medium in the recording demagnetization _{(Br × t ma g / Hc} ) ( Matsumoto HikariIsao et al., "Magnetic recording Engineering", Kyoritsu Shuppan, Chapter 51
page). Here, Hc, Br, and t _mag represent the coercive force, residual magnetic flux density, and magnetic film thickness of the medium, respectively. FIG. 6 shows the result of plotting the OW3 dB reduction length against Brt / Hc by the same method as described above. From FIG. 6, OW3d
It can be seen that the B reduction length is 5 Brt / Hc. Therefore, in order to secure a sufficient OW characteristic, it is necessary to set the recording current reversal distance to 5 Brt / Hc or less. This is what the expression (2) means.

[0014] In addition, in the OW characteristic measurement conditions of the above-mentioned t _r, t _f
Is changed and OW (N ′ / N) is plotted with respect to the 2F frequency, and the OW characteristic deterioration start frequency FW is defined as shown in FIG. 7. FIG. 8 shows the 1 / (t _r + t _f ) dependence of FW. It can be seen from FIG. 8 that the following relationship holds. FW = 1 / (t _r + t _f ) This is because when recording is performed at a frequency of 1 / (t _r + t _f ) or higher, adjacent recording current inversions interfere and the recording current setting value cannot be maintained. Then it is speculated. The recording current value attenuates with the set recording frequency, and it becomes difficult to maintain a sufficient OW characteristic mainly due to a decrease in the recording magnetic field.

[0015]

The present invention will be described in detail below with reference to examples. [Embodiment 1] As a magnetic storage device, a magnetic storage device whose conceptual diagram is shown in FIG. 13 was prepared. This magnetic storage device includes a magnetic recording medium 2 for recording magnetic information, a magnetic head 10 for recording and reproducing information on and from the magnetic recording medium 2, and a recording amplifier 6 for recording a recording signal to a recording magnetic head. Circuit 16,
A reproducing circuit 19 including a preamplifier 17 and a discrimination circuit 18 for processing a signal from a reproducing head, a controller 14, C
It has a well-known configuration including the PU 15 and the like. CPU15
Under the control of the magnetic head 10, the magnetic head 10 moves in accordance with a command issued from the controller 14 to the positioning circuit 13.
Is positioned on the desired track 11, and magnetic information is recorded or reproduced on that track.

As described in the section of operation, the magnetization transition width Lo proportional to the recording demagnetizing field (Br × t _mag / Hc) in the medium.
When the recording current reversal distances (t _r × v) and (t _f × v) are smaller than (≈πa), the width L of the magnetization transition region actually formed on the medium is Lo as shown in FIG. Matches However, on the contrary, the recording current reversal distance (t _r
Xv) and (t _f × v) are large, the width L of the magnetization transition region formed on the medium is (t _r ×
v) and (t _f × v). The magnetization transition part corresponds to the recording current reversal part, and a sufficient recording magnetic field is not generated. Therefore, if the magnetization transition width becomes large, it becomes difficult to secure sufficient OW characteristics. Further, by further setting the recording frequency to 1 / (t _r + t _f ) or less, O
The decrease in W can be suppressed.

In the present embodiment, the magnetic memory device shown in FIG. 13 was used to perform saturated magnetic recording on a medium of πa = 204 nm at a recording density of 2 gigabits per square inch, and the overwrite characteristics were examined. Here, the linear recording density is 117 kB
PI (RLL 1,7 code), track density 17kT
It was set as PI. That is, the magnetization reversal density is 88 kFCI and the track pitch is 1.5 μm. As shown in FIG. 4, the relative velocity between the head and the medium v = 25.6 m / se
c, recording current reversal distance [(t _r + t _f ) × v / 2] <20
When recorded under the condition of 4 nm, that is, (t _r + t _f ) / 2 <8.0 nsec, deterioration of the OW characteristic could be suppressed, but [(t _r + t _f ) × v / 2] = 269n
m, that is, [(t _r + t _f ) × v / 2] <20 when recorded under the condition of (t _r + t _f ) /2=10.5 nsec.
A deterioration of the overwrite characteristic of 4.3 dB was recognized as compared with the case of 4 nm.

[Embodiment 2] FIG. 9 shows an equivalent circuit diagram of a recording amplifier including a magnetic head. V _5, timed recording by V _8, determines the waveform pattern of recording current by providing data of high and low level _{V 1, V 2, V 3} , V 4. The power supply voltage applied to the recording amplifier corresponds to the absolute value of V _E. A concrete operation state of the recording amplifier is shown in FIG. In state A, the transistor Q ₁ ,
High level on the base of Q ₄ , transistors Q ₂ and Q ₃
Gives a low level to the base. At this time, the transistors Q ₁ and Q ₄ are turned on and the transistors Q ₂ and Q ₃ are turned off, and the recording current I _w constantly flows from left to right as shown in the figure. Contrary to the state A, the state C is the transistor Q ₁ , Q ₄
Of the transistor Q ₂ and Q ₃ is given a high level. At this time, the transistors Q ₁ and Q ₄ are turned off, Q ₂ and Q ₃ are turned on, and the recording current I
_As shown in the figure, _w flows from right to left in the opposite direction to state A. State B shows a transient state from state A to state C. Each L _H inductance and the resistance value of the recording head, and R _H, transistors Q _1, Q ₂ of the base-emitter voltage of the respective V _BEQ1, V _BEQ2. R ₁ and R ₂ , Q
By arranging resistors and transistors having the same characteristics in ₁ and Q ₂ , respectively, the base potential hi of the transistors Q ₁ and Q ₂ is hi.
The gh and low levels can take almost the same value. When the emitter potentials of Q ₁ and Q ₂ in the state B are e ₁ and e ₂ , respectively, the following equation holds.

E ₁ = V _L1 −V _BEQ1 , e ₂ = V _H1 −V _BEQ2 Here, _assuming that V _BEQ1 and V _BEQ2 are substantially equal, | e ₁ −e ₂ | = V _H1 −V _L1 . Here, when _{V B = V H1 -V L1,} V B = R H · I w (t) + L H · dI w (t) / dt becomes a differential equation is established. However, I _w (t) is the time t
Is the recording current value at. Solving _{this, I w (t) = V} B / R H - (V B / R H + I w) exp (-R H / L H
・ T). However, I _w is the recording current value in the state A. t _r, when the t _f is defined as a time across the 10% and 90% of the recording current reversal amount, the following equation (4) is obtained.

[0020] _{t r, t f = t [} I w (t) = 0.8I w] -t [I w (t) = - 0.8I w] = (L H / R H) · Ln [1 + 1.6I w / (V _B / _RH −0.8I _w )] (4) Alternatively, t _a ≡ (t _r + t _f ) / 2 = t [I _w (t) = 0.8 I _w ] -t [I _w (t _{) = - 0.8I w] = (} L H / R H) · Ln [1 + 1.6I w / (V B / R H -0.8I w)] By transforming this equation is obtained.

I _w = (V _B / R _H ) / [1.6 / [exp (t _a R _H / L _H ) −1] +0.8] (5) Experimental verification of the above theory is shown below. . Actually, in most cases, as a result of the recording system optimization, V _B corresponds to about half the power supply voltage V _E given to the recording amplifier. 8.6V and 5.2
For the recording amplifier driven by the power supply voltage of V, V _B is set to 4.2 V and 2.2 V, respectively, the number of coil windings of the head is changed to 17, 30 and 40 turns, and the recording head and recording are performed. Inductance (0 to 0
T _r by inserting a 1.2μH), was varied t _f.
The value of t _r calculated by the equation (4) and the value of t _r calculated by the experiment (t _r
FIG. 11 shows a plot of the relationship of + t _f ) / 2. The figure shows that the experiment fits well with the theory.

In the magnetic storage device of 2 gigabits or more per square inch, high coercive force of the medium is required. A recording / reproducing experiment was conducted using a recording head using a high saturation magnetic flux density material Co-Ni-Fe (Bs = 1.7T) for a medium having a coercive force Hc = 2.3 to 3.8 kOe. FIG. 12 shows the results of plotting the magnetomotive force against Hc such that the reproduction output saturates as the magnetomotive force increases. From this result, the magnetomotive force required for recording is 0.53 Aturn for the medium with Hc = 2.5 kOe and 0.62 Atu for Hc = 3 kOe.
rn, Hc = 3.5 kOe, 0.73 Aturn was found. That is, the number of recording head turns is N,
Half of the supply voltage V _E to give V _B to the recording amplifier, i.e. the _{V B = V E / 2,} Hc from (5) = 2.5KO
(V _E · N / 2R _H ) / [1.6 / [exp (t _a R _H / L _H ) -1] +0 for e.
8]> 0.53 Hc = 3 kOe (V _E N / 2R _H ) / [1.6 / [exp (t _a R _H / L _H ) -1] +0.
8]> 0.62 Hc = 3.5 kOe, (V _E N / 2R _H ) / [1.6 / [exp (t _a R _H / L _H ) -1] +0.
It turns out that 8]> 0.73 is required. For example, Hc = 2.9
For medium of kOe, V _E = 8.2V, N = 17 turns,
R _H = 18.6Ω, L _H = 0.22 μH, (t _r + t _f ) / 2
= 5.1 nsec, (V _E · N / 2R _H ) / [1.6 / [exp (t _a R _H / L _H ) −1] +0.
8] = 4.4, and the good OW characteristics as I _w = 40mAop obtained.

[0023]

According to the present invention, in a magnetic storage device, the recording head material is not changed, the distance between the magnetic head and the magnetic recording medium is not particularly reduced, and the OW characteristic is not deteriorated. , High frequency recording can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of corresponding states of a recording current waveform and a magnetization transition portion during high frequency recording according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a corresponding state of a recording current waveform and a magnetization transition portion during high frequency recording according to a conventional technique.

FIG. 3 is an equivalent circuit diagram of a recording system used in an experiment for examining the dependence of OW (N ′ / N) on t _r and t _f .

FIG. 4 is a recording current reversal distance of OW (N ′ / N) [(t _r + t
_f ) xv / 2] dependence.

FIG. 5 is a diagram showing πa dependence of OW3 dB reduction length.

FIG. 6 is a graph showing Brt / Hc dependency of OW3 dB reduction length.

FIG. 7 is a definition diagram of an OW characteristic deterioration start frequency FW.

FIG. 8: 1 / (t _r + of OW characteristic deterioration start frequency FW)
t _f ) diagram showing dependency.

FIG. 9 is an equivalent circuit diagram of a recording amplifier including a recording head.

FIG. 10 is an operation state diagram of the recording amplifier.

FIG. 11 is a diagram showing the correspondence between the experimentally measured value and the calculated value of the recording current reversal time.

FIG. 12 is a diagram showing a relationship between a coercive force of a magnetic recording medium and a magnetomotive force required for recording.

FIG. 13 is a conceptual diagram of a magnetic storage device.

[Explanation of symbols]

1: Recording current waveform, 2: Magnetic recording medium, 3: Recording magnetization direction, 4: Magnetization transition part, 5: Recording head, 6: Recording amplifier, 7: Additional inductance, 14: Controller, 1
5: CPU, 16: recording circuit, 19: reproducing circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiro Shiroishi 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. Hitachi Central Research Laboratory (72) Inventor Shinya Matsuoka 2880 Kozu, Odawara City, Kanagawa Stock Company, Hitachi Storage Systems Division

Claims (9)

[Claims] 1. A magnetic storage method for performing saturated magnetic recording on a magnetic recording medium at a recording density of 2 gigabits per square inch or more by passing a rectangular wave recording current through a magnetic head, when switching is performed while the recording current increases. The time between 10% and 90% of the recording current reversal amount is the rise time t _r , and the time between 10% and 90% of the recording current reversal amount when switching while the recording current is decreasing is the fall time t _r . _f , relative velocity between head media v,
A magnetic storage method characterized in that the following expression is satisfied, where L is the width of magnetization reversal on the medium. v × (t _r + t _f ) / 2 ≦ L 2. A magnetic recording medium for storing magnetic data at a recording density of 2 gigabits per square inch or more and a magnetic head for recording / reproducing a signal, wherein the magnetic recording medium is supplied with a rectangular wave recording current. In a magnetic storage device for performing saturated magnetic recording on a recording medium, during the saturated magnetic recording, a rise time t _{r is} a time between crossing 10% and 90% of a recording current reversal amount when switching while increasing a recording current. Assuming that the fall time t _f is the time between 10% and 90% of the recording current reversal amount when the switching is performed while the current is decreasing, the head medium relative velocity is v, and the magnetization reversal width on the medium is L A magnetic storage device characterized by satisfying: v × (t _r + t _f ) /
2 ≦ L 3. A magnetic storage method for performing saturated magnetic recording on a magnetic recording medium at a recording density of 2 gigabits per square inch or more by passing a rectangular wave recording current through a magnetic head, when switching is performed while the recording current increases. The time between 10% and 90% of the recording current reversal amount is the rise time t _r , and the time between 10% and 90% of the recording current reversal amount when switching while the recording current is decreasing is the fall time t _r . _f , relative velocity between head media v,
A magnetic storage method characterized by satisfying the following formula when the medium coercive force is Hc, the medium saturation magnetic flux density is Br, and the medium magnetic film thickness is t _mag . v × (t _r + t _f ) / 2 ≦ 5 × Br × t _mag / Hc 4. A magnetic recording medium for storing magnetic data at a recording density of 2 gigabits per square inch or more and a magnetic head for recording / reproducing a signal, wherein a rectangular wave recording current is applied to the magnetic head to cause the magnetic field. In a magnetic storage device for performing saturated magnetic recording on a recording medium, during the saturated magnetic recording, a rise time t _{r is} a time between crossing 10% and 90% of a recording current reversal amount when switching while increasing a recording current. When switching is performed while the current is decreasing, the time during which the recording current reversal amount crosses 10% and 90% is the fall time t _f , the head-medium relative velocity is v, the medium coercive force is Hc, and the medium saturation magnetic flux density is Br. A magnetic storage device characterized by satisfying the following formula when the magnetic film thickness of the medium is t _mag . v × (t _r + t _f ) / 2 ≦ 5 × Br × t _mag / Hc 5. A recording current reversal at the time of switching while increasing the recording current when performing saturated magnetic recording at a recording density of 2 gigabits per square inch or more on a magnetic recording medium by supplying a rectangular wave recording current to the magnetic head. Quantity 1
The time between 0% and 90% crossing is the rise time t _r , the time between 10% and 90% of the recording current reversal amount when the recording current is switching while decreasing, and the falling time t _{f is} the recording frequency. A magnetic storage method characterized by satisfying the following expression when f _w is set. f _w ≤ 1 / (t _r + t _f ) 6. A magnetic recording medium for storing magnetic data at a recording density of 2 gigabits or more per square inch and a magnetic head for recording / reproducing a signal, wherein a rectangular wave recording current is passed through the magnetic head to produce the magnetic field. In a magnetic storage device for performing saturated magnetic recording on a recording medium, during the saturated magnetic recording, a rise time t _{r is} a time between crossing 10% and 90% of a recording current reversal amount when switching while increasing a recording current. A magnetic memory characterized by satisfying the following formula when the fall time t _f is the time between 10% and 90% of the recording current reversal amount when the current is decreasing and the recording frequency is f _w. apparatus. f _w ≤ 1 / (t _r + t _f ) 7. A magnetic recording medium having a coercive force of 2.5 kOe or more and a recording density of 2 gigabits or more per square inch, a magnetic head for recording and reproducing signals, and a recording current flowing through the magnetic head. In a magnetic storage device which includes a recording amplifier to which a power supply voltage of V _E is applied and which performs a saturated magnetic recording on the magnetic recording medium by supplying a rectangular wave recording current to the magnetic head, the recording current at the time of the saturated magnetic recording. Of the recording current reversal amount when switching while increasing while rising time t _r , and 10% and 90% of the recording current reversal amount when switching while decreasing the recording current. Is the fall time t _f , t _a = (t _r + t _f ) / 2, L _{H is} the inductance of the recording head, R _{H is} the resistance, and N is the number of turns of the coil. A magnetic storage device characterized by satisfying the relationship of (V _E N / 2R _H ) / [1.6 / [exp (t _a R _H / L _H ) -1] +0.
8]> 0.53 8. A magnetic recording medium having a coercive force of 3 kOe or more and a recording density of 2 gigabits or more per square inch, a magnetic head for recording and reproducing signals, and a V for supplying a recording current to the magnetic head. _In a magnetic storage device that includes a recording amplifier to which a power supply voltage of _E is applied, and performs a saturated magnetic recording on the magnetic recording medium by supplying a rectangular wave recording current to the magnetic head, when performing the saturated magnetic recording,
The rising time t _r is the time between 10% and 90% of the recording current reversal amount when switching while the recording current increases, and 10% and 90% of the recording current reversal amount when switching while the recording current decreases. When the crossing time is the fall time t _f , t _a = (t _r + t _f ) / 2, the inductance of the recording head is L _H , the resistance is R _H , and the number of turns of the coil is N, the following equation is obtained. A magnetic storage device characterized by satisfying a relationship. (V _E N / 2R _H ) / [1.6 / [exp (t _a R _H / L _H ) -1] +0.
8]> 0.62 9. A magnetic recording medium having a coercive force of 3.5 kOe or more and a recording density of 2 gigabits per square inch, a magnetic head for recording / reproducing signals, and a recording current flowing through the magnetic head. In a magnetic storage device which includes a recording amplifier to which a power supply voltage of V _E is applied and which performs a saturated magnetic recording on the magnetic recording medium by supplying a rectangular wave recording current to the magnetic head, the recording current at the time of the saturated magnetic recording. Of the recording current reversal amount when switching while increasing while rising time t _r , and 10% and 90% of the recording current reversal amount when switching while decreasing the recording current. Is the fall time t _f , t _a = (t _r + t _f ) / 2, L _{H is} the inductance of the recording head, R _{H is} the resistance, and N is the number of turns of the coil. A magnetic storage device characterized by satisfying the relationship of (V _E N / 2R _H ) / [1.6 / [exp (t _a R _H / L _H ) -1] +0.
8]> 0.73