JPH0773417A - Magneto-resistance effect type magnetic head and magnetic disk device - Google Patents

Abstract

PURPOSE:To provide a magneto-resistance effect type magnetic head which has not a differential detection constitution and removes the thermal noise in real time. CONSTITUTION:A bias layer 5 close to a magneto-resistance element 7 is used as the temperature detecting means, and the detected signal is outputted through electrodes 10B and 10C, and this output is applied to the output of the magneto- resistance element 7 by a differential amplifier 22 after being corrected by an amplifier 21. Thus, the thermal noise superposed on the magneto-resistance element 7 is corrected. Consequently, the throughput of data is improved because the thermal noise superposed on the magneto-resistance effect type magnetic head is removed in real time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect magnetic head (MR head), and more particularly to a magnetoresistive effect magnetic head due to temperature fluctuation factors such as frictional heat when the MR head contacts a magnetic recording medium. The present invention relates to an MR head that can eliminate output fluctuations due to head temperature fluctuations.

[0002]

2. Description of the Related Art An MR head utilizing an MR element for reproduction has been proposed as a means for increasing the recording density of a magnetic disk. The MR element has a resistance that changes according to a change in a magnetic field, and has a higher reproduction sensitivity than an inductive head that has been conventionally used. During reproduction, a constant current is passed through the MR element to detect the resistance change as a voltage change. In addition, MR
Since the head is not writable, it is actually used as an MR inductive composite head (hereinafter also referred to as a magnetic head or MR / IND head) in combination with an inductive head used for writing. By the way, in the magnetic head, as shown in FIG. 5, the magnetic head and the medium may come into direct or indirect contact with each other due to protrusions of the disk, dust, or the like. At the contact point, frictional heat causes a rapid temperature rise. If the contact point is near the MR element, the MR
It is known that the resistance of the element changes and the output changes. This output fluctuation will be collectively referred to as thermal noise. An example of thermal noise is shown in FIG. In this way, the thermal noise 72 is additively added to the data signal 71. As a conventional technique excluding this thermal noise,
JP-A-2-154310, JP-A-2-54403
There is one described in the publication. The former uses two MR elements.
This is a method of canceling the thermal noise by providing two MR elements in a differential type and performing differential detection. The latter detects the positive envelope 73 and the negative envelope 74 shown in FIG. 7 from the detection signal on which the thermal noise is superimposed, and detects the thermal noise from this envelope. The obtained thermal noise is used to separate the thermal noise from a signal containing the thermal noise.

[0003]

Among the prior arts, the former has a problem that it is difficult to narrow the track width because of the structure because the track width of two MR elements is required. The latter is not limited to narrowing the track width, but it takes time to process the signal. For example, reading the address signal of the track and checking whether the read address is an address to be accessed for a predetermined time. There may be the problem that it cannot be processed within. For this reason,
The circuit that removes the thermal noise does not normally operate.When a data error is detected, it is possible that the thermal noise may be the cause. Conceivable.
However, in this case, real-time processing cannot be performed and data throughput deteriorates. Further, when the thermal noise changes abruptly as shown in FIG. 7, there is a problem that the envelope cannot be obtained correctly, the input signal cannot be completely corrected, and an error may occur in the data. It is an object of the present invention to provide a magnetoresistive effect type magnetic head which does not have a differential detection structure and removes thermal noise in real time.

[0004]

To solve the above problems, the present invention provides a magnetoresistive magnetic head having a magnetoresistive element for detecting magnetism by utilizing the magnetoresistive effect. The temperature detecting means is provided in the vicinity and detects temperature information of the magnetoresistive element, and the output means outputs the detected temperature information. Further, instead of separately providing the temperature detecting means, the bias layer is commonly used for temperature detection.

[0005]

By placing the temperature detecting means close to the magnetoresistive element, the temperature of the temperature detecting means becomes substantially equal to the temperature of the magnetoresistive element. Therefore, since the resistance change due to the temperature change of the temperature detecting means is proportional to the resistance change due to the temperature change of the magnetoresistive element, by appropriately amplifying the output from the temperature detecting means and the output of the magnetoresistive element, the difference can be obtained. Temperature compensation can be performed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 shows only the magnetoresistive element portion related to the invention in the structure of the magnetic head according to the present invention for the sake of simplicity. The MR element 7 reads from a track other than the track to be read. The upper shield part for preventing the MR element 7 from detecting the magnetic field, the recording head, etc. are not shown. A material modifying layer 2, a lower shield layer 3, a separation layer 4, and a bias layer 5 thereon are provided on a slider material 1 on which a magnetic head is mounted, and an insulation material or a high resistance material separation layer 6 is provided. An MR film (MR element) 7 is provided via the. The material modification layer 2 is for improving the adhesiveness between the slider material 1 and the lower shield layer 3. Lower shield layer 3
Is for preventing the MR element 7 from detecting a magnetic field from a track other than the track that the MR element 7 is trying to read. The separation layer 4 is for magnetically separating the lower shield layer 3 and the bias layer 5. The bias layer 5 is for applying a bias magnetic field in a fixed direction to the MR element, and the magnetic field applied to the MR element 7 is generated by passing a current through the bias layer 5. The bias magnetic field is provided in order to optimize the sensitivity of the MR element 7. This is because the separation layer 6 electrically separates the bias layer 5 and the MR element 7 from each other, and makes it easier to control the current flowing through each. The present invention can be applied to an MR head that does not have the separation layer 6. On the MR film 7, a magnetic domain control film 8 for reducing Barkhausen noise caused by the movement of the domain wall, a film 9 provided for manufacturing reasons to define the track width, and both ends of the MR film 7. There are electrodes 10A, 10B provided on the. The electrode 10B is connected to the MR film 7 via the magnetic domain control layer 8 which is a conductor. The bias layer 5 may be a shunt bias, which is a method in which a current is applied to a conductor to generate a magnetic field, or a soft magnetic film combined type, which is a method in which a current is applied to a soft magnetic material, and the bias method is not limited. Further, electrodes are provided at both ends of the bias layer 5, but the electrode on one side is shared with the electrode (electrode A) of the MR film 7 in order to reduce the lead lines. In addition, the bias layer 5
When the MR film 7 and the bias layer 5 are separately used as currents when the temperature detection film is commonly used, it becomes easy to detect the temperature separately from the signal. In this configuration, the bias layer 5, the MR layer 7, the magnetic domain control layer 8, the electrode 1
0 is a conductive material. The separation layer 6 of the MR film 7 and the bias layer 5 has a thickness of about 5 to 50 nm, and it is considered that the MR film 7 and the bias layer 5 have almost the same temperature. The isolation layer 6 is preferably an insulating material, but may be a high resistance metal.

Next, a circuit configuration example for eliminating thermal noise will be described with reference to FIG. Fig. 1 shows the constant current drive system,
There is no need to limit this. When a constant current is applied to each of the MR film 7 and the bias layer 5, a voltage corresponding to a resistance change due to a temperature change appears at both ends of the MR film 7 and the bias layer 5. After amplifying the AC components of these voltages with the differential detector 20, the MR
The amplifier 21 is adjusted so as to correct the difference in the rate of change in resistance with respect to the temperature of the film 7 and the bias layer 5 and the change in current.
The differential amplifier 22 cancels only the thermal noise. The MR film 7 detects a magnetic signal and thermal noise, and the bias layer 5 detects a change due to thermal noise, but does not detect a magnetic signal. Therefore, by differentially amplifying the signal from the MR film 7 and the signal from the bias layer 5, thermal noise is removed and the magnetic signal detected by the MR film 7 is not changed. Next, another structural example of the head of the present invention will be described with reference to FIGS. 3 and 4 are views of the magnetic head as seen from the side of the magnetic head that contacts the disk. In FIG. 3, the temperature detection layer 12 is provided separately from the bias layer 5 in FIG. 1, and the temperature detection layer 12 is provided below the conventional magnetoresistive effect magnetic head via the separation layer 11. . Figure 4
This is an example in which the temperature detection layer 12 is provided when the magnetic domain control layer 8 is an insulating material. As described above, the main object of the present invention is to provide the temperature detecting layer in the vicinity of the MR layer, and in carrying out the present invention, there is no limitation due to the configuration, arrangement, material, process, etc. of the head. Absent. FIG. 6 shows a schematic configuration of a magnetic disk device equipped with a magnetic head and a thermal noise guarantee amplifier according to the present invention. The operation will be described. MR / I
The reproduction output from the ND head 61 is supplied to the R / W preamplifier 63.
If the reproduced signal is a signal in the data area after removing the thermal noise with the above-mentioned thermal noise guarantee amplifier,
The signal is sent to the recording / reproducing discrimination system 64, and in the case of a signal in the servo signal area, the signal is sent to the position signal demodulation system 65, and based on the signal, follow-up control of the magnetic head or seek operation etc. It is performed by the control system 66. According to the present invention, it is possible to prevent a data error due to thermal noise and a malfunction of position control.

[0009]

As described above, according to the present invention, the thermal noise superimposed on the magnetoresistive magnetic head can be eliminated in real time by the output of the temperature detecting means, so that the data throughput can be improved. Can be achieved. Also, even if a sudden thermal noise occurs, the data will be corrected correctly, so
Data reliability is improved. Further, the MR head can be used even in a disk in which the head and the disk are frequently contacted with each other, and it is possible to remedy what was conventionally regarded as a defective product due to the poor flatness of the disk surface, so that the disk yield is improved. There is also.

[Brief description of drawings]

FIG. 1 is a circuit diagram for explaining the operation of an MR head according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment of an MR head according to the present invention.

FIG. 3 is a configuration diagram of another embodiment of the MR head according to the present invention.

FIG. 4 is a configuration diagram of another embodiment of the MR head according to the present invention.

FIG. 5 is an explanatory diagram of a contact state between a magnetic head and a disk.

FIG. 6 is a block diagram of a disk device.

FIG. 7 is an explanatory diagram of a reproduced signal when thermal noise occurs.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Slider, 2 ... Material modification layer, 3 ... Lower shield part, 4 ... Separation layer, 5 ... Bias layer, 6 ... Separation layer, 7 ... M
R, 8 ... Magnetic domain control layer, 9 ... Track width control layer, 10 ... Electrode, 11 ... Separation layer, 12 ... Temperature detection layer, 13 ... Magnetic domain control separation layer, 20 ... Differential amplifier, 21 ... Amplifier, 22 ... Difference Motion amplifier, 23 ... Separation layer.

Claims (3)

[Claims] 1. A magnetoresistive magnetic head having a magnetoresistive element for detecting magnetism by utilizing a magnetoresistive effect, the temperature being provided in the vicinity of the magnetoresistive element, for detecting temperature information of the magnetoresistive element. A magnetoresistive effect magnetic head comprising: a detection means and an output means for outputting the detected temperature information. 2. A magnetoresistive effect magnetic head according to claim 1, wherein a bias layer for applying a bias magnetic field to said magnetoresistive element, and a current input / output means for flowing a current for generating a bias magnetic field through said bias layer. And the bias layer has a function of the temperature detection means, and the current input / output means has a function of the output means. 3. A magnetoresistive effect magnetic head according to claim 1 or 2, wherein temperature-dependent noise contained in a signal output by the magnetoresistive element is generated based on temperature information output by the output means. And a means for removing the magnetic disk apparatus.