（Institutute of Physics of Chinese Academy of Sciences，Beijing 100000，China）
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DOI:
10.7502/j.issn.1674-3962.2013.06.02
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Abstract:
A typical magnetic tunnel junction (MTJ) consists of a thin insulating layer (a tunnel barrier)， sandwiched by two ferromagnetic electrode layers. When the relative magnetic configuration of both ferromagnetic electrode layers changes from parallel state to antiparallel state with external magnetic field， the resistance of MTJ would become high from low， exhibiting tunnel magnetoresistance (TMR) due to spindependent electron tunnelling. Amorphous AlOx barrier MTJs were extensively studied and have been used in magnetoresistance random access memory (MRAM) and read heads of hard disk drives， since the discovery of roomtemperature TMR in 1995. However， the spin electronic devices development of the nextgeneration highspeed， lowpowerconsumption and highperformance need much higher TMR ratio and a novel structure. In 2001， the firstprinciple calculation predicted that the TMR ratio of epitaxial Fe (001)/MgO (001)/Fe (001) MTJs would be over 1 000%， due to spin filter effect of MgO barrier for different symmetry spin polarized electron. In 2004 TMR ratios of about 200% were obtained in MTJs with a singlecrystal MgO (001) barrier or a textured MgO (001) barrier. In 2008， the TMR ratio of 604% has been reported in pseudospinvalve MTJs with core structure of CoFeB/MgO/CoFeB. Recently， Quantum well (QW) resonances tunneling and spindependent Coulomb blockade magnetoresistance (CBMR) effect in MgObarrier MTJs were proposed and demonstrated in theories and experiments. Magnetic sensors， MRAM， spin nanooscillator and microwave detector based on MTJs have attracted attention of electron science and devices. In the paper we briefly introduced the investigation and development of magnetic tunnel junction material and its device applications.