T8480 輸出模塊

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TMR 效應(yīng)就是一種關(guān)于自旋極化運(yùn)輸過(guò)程的現(xiàn)象。TMR 效應(yīng)的產(chǎn)生機(jī)理是自旋相關(guān)的隧穿效應(yīng)，TMR的結(jié)構(gòu)為鐵磁層/非磁絕緣層/鐵磁層(FM//FM)的三明治結(jié)構(gòu)。飽和磁化時(shí)，兩鐵磁層的磁化方向互相平行，而通常兩鐵磁層的矯頑力不同。因此反向磁化時(shí),矯頑力小的鐵磁層磁化矢量首先翻轉(zhuǎn)，使得兩鐵磁層的磁化方向變成反平行。
電子從一個(gè)磁性層隧穿到另一個(gè)磁性層的隧穿幾率與兩磁性層的磁化方向有關(guān)。若兩層磁化方向互相平行，則在一個(gè)磁性層中多數(shù)自旋子帶的電子將進(jìn)入另一磁性層中多數(shù)自旋子帶的空態(tài)，少數(shù)自旋子帶的電子也將進(jìn)入另一磁性層中少數(shù)自旋子帶的空態(tài)，總的隧穿電流較大，若兩磁性層的磁化方向反平行，情況則剛好相反，即在一個(gè)磁性層中，多數(shù)自旋子帶的電子將進(jìn)入另磁性層中少數(shù)自旋子帶的空態(tài)，而少數(shù)自旋子帶的電子也將進(jìn)入另一磁性層中多數(shù)自旋子帶的空態(tài)，這種狀態(tài)的隧穿電流比較小。因此，隧穿電導(dǎo)隨著兩鐵磁層磁化方向的改變而變化，碰化矢量平行時(shí)的電導(dǎo)高于反平行時(shí)的電導(dǎo)。通過(guò)施加外磁場(chǎng)可以改變兩鐵磁層的磁化方向，從而使得隧穿電阻發(fā)生變化，導(dǎo)致 TMR 效應(yīng)的出現(xiàn)。
當(dāng)磁體在TMR傳感器上旋轉(zhuǎn)時(shí)，自由層的磁化方向跟隨磁體的磁場(chǎng)方向，元件的電阻不斷變化。由于電阻值與釘扎層和自由層的磁化方向之間的相對(duì)角度成正比，因此TMR元件可以用作角度傳感器
因?yàn)門(mén)MR傳感器的電陽(yáng)值與釘扎層和自由層的磁化方向之間的相對(duì)角度成正比，所以它可以進(jìn)行360%角度檢測(cè)。另外TMR傳感器的輸出是霍爾元件的 500 倍，而且功耗低(推薦條件下為 5mw)，非常適合用作汽車(chē)應(yīng)用的傳感器。例如，它們可以替代使用霍爾元件的傳統(tǒng)角度傳感器，如汽車(chē)轉(zhuǎn)向角度傳感器或 EPS(電動(dòng)助力轉(zhuǎn)向)電機(jī)角度傳感器。同時(shí)TMR傳感器的低溫漂性非常適合汽車(chē)以及各類(lèi)工業(yè)設(shè)備。

T8480

The TMR effect is a phenomenon related to spin polarization transport process. The mechanism of TMR effect is spin-dependent tunneling effect, and the structure of TMR is a sandwich structure of ferromagnetic layer/non-magnetic insulation layer/ferromagnetic layer (FM//FM). In saturation magnetization, the magnetization direction of the two ferromagnetic layers is parallel to each other, and usually the coercivity of the two ferromagnetic layers is different. Therefore, when the magnetization is reversed, the magnetization vector of the ferromagnetic layer with low coercivity is flipped first, so that the magnetization direction of the two ferromagnetic layers becomes anti-parallel.
The tunneling probability of electrons from one magnetic layer to another is related to the direction of magnetization of the two magnetic layers. If the magnetization direction of the two layers is parallel to each other, most of the electrons of the spin belt in one magnetic layer will enter the empty state of the majority of the spin belt in the other magnetic layer, and a few of the electrons of the spin belt will also enter the empty state of the few spin belt in the other magnetic layer, the total tunneling current is larger, if the magnetization direction of the two magnetic layers is anti-parallel, the situation is just the opposite, that is, in a magnetic layer, Most of the electrons in the spin belt will enter the empty state of the few spin belts in the other magnetic layer, and the few electrons in the spin belt will also enter the empty state of the most spin belts in the other magnetic layer, which has a relatively small tunneling current. Therefore, the tunneling conductance changes with the direction of magnetization of the two ferrospheres, and the conductance when the collision vector is parallel is higher than that when it is antiparallel. By applying an external magnetic field, the direction of magnetization of the two ferromagnetic layers can be changed, which changes the tunneling resistance and leads to the appearance of TMR effect.
When the magnet rotates on the TMR sensor, the magnetization direction of the free layer follows the magnetic field direction of the magnet, and the resistance of the element constantly changes. Since the resistance value is proportional to the relative Angle between the direction of magnetization of the pinned layer and the free layer, the TMR element can be used as an Angle sensor
Because the electropositive value of the TMR sensor is proportional to the relative Angle between the direction of magnetization of the pinned layer and the free layer, it can perform 360% Angle detection. In addition, the output of the TMR sensor is 500 times that of the Hall component, and the power consumption is low (5mw under recommended conditions), making it ideal for use as a sensor for automotive applications. For example, they can replace traditional Angle sensors that use Hall components, such as automotive steering Angle sensors or EPS(electric Power steering) motor Angle sensors. At the same time, the low temperature bleachability of TMR sensors is very suitable for automobiles and various industrial equipment.

T8480