SPIN-ORBIT TORQUE MAGNETIC RANDOM ACCESS MEMORY AND METHOD OF WRITING THE SAME

專利類型

發明

專利國別 (專利申請國家)

美國

專利申請案號

15/374,606

專利證號

US 9,666,256

專利獲證名稱

SPIN-ORBIT TORQUE MAGNETIC RANDOM ACCESS MEMORY AND METHOD OF WRITING THE SAME

專利所屬機關 (申請機關)

國立清華大學

獲證日期

2017/05/30

技術說明

一種自旋軌道扭力式磁性隨存記憶體及其寫入方法。該自旋軌道扭力式磁性隨存記憶體包含設於基板並具磁性自由層的自旋軌道扭力式記憶胞。磁性自由層包括彼此接觸的鐵磁性第一金屬膜及呈自旋霍爾效應的第二金屬膜。第一金屬膜具一足以使磁性自由層具一介於±0.9之殘留磁化量對飽和磁化量的比值的厚度。該比值是在沿著第一金屬膜之難軸對磁性自由層依序提供與釋放一足以使磁性自由層達該飽和磁化量的第一外加磁場後所達成，從而令第一金屬膜在沿著其難軸對磁性自由層提供一遠小於第一外加磁場的第二外加磁場與一交流脈衝電訊號以達其所產生之臨界電流密度以上時具3級以上的磁域。 According to one aspect of the present disclosure, a spin-orbit torque magnetic random access memory (SOT-MRAM) may be provided. The SOT-MRAM includes a substrate and an SOT memory cell. The SOT memory cell is disposed on the substrate and includes a magnetic free layer. The magnetic free layer includes a first metal film exhibiting ferromagnetic characteristics, and a second metal film contacting the first metal film for generating a spin-Hall effect. The first metal film has a thickness sufficient to allow the magnetic free layer, after being applied with a first external magnetic field which is subsequently removed, to have a remanent-to-saturated magnetization ratio ranging from -0.9 to 0.9. The first metal film, upon being applied with a second external magnetic field and an electric pulse, has multiple magnetic domains when a current density resulting from the electric pulse is greater than a critical value. The magnetic free layer has a magnetic switching behavior when the current density reaches the critical value. The second external magnetic field is provided in a direction identical to the first external magnetic field and is less in magnitude than the first external magnetic field. According to another aspect of the present disclosure, a method of writing the aforesaid SOT-MRAM includes the steps of: applying a first external magnetic field to the magnetic free layer of the SOT memory cell and subsequently removing the first external magnetic field, such that the first metal film has a remanent-to-saturated magnetization ratio ranging from -0.9 to 0.9; and applying a second external magnetic field and a first electric pulse to the magnetic free layer of the SOT memory cell, such that the second metal film generates a first self-spinning current via the spin-Hall effect and reverses magnetic moments of the first metal film upon a resulting current density reaching the critical value, wherein the magnetic free layer has one of positively-saturated and negatively-saturated magnetizations upon the current density reaching the critical value.

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