Properties Of Fept Films Deposited On Si(001) Substrates

As memory technology continues to advance,the size of memory devices has decreased significantly.L1₀-FePt has a particularly large uniaxial magnetocrystalline anisotropy,used to store information,can achieve higher storage area density.Inside the L1₀-FePt material,there is an orbital hybridization between the free electrons of Fe atoms and Pt atoms,which makes the room temperature coercive force H_c of granular L1₀-FePt can reach 70 kOe experimentally.Made into small particle film,it can be used for ultra-high density data storage.But the switching field is too large,and conventional methods cannot rewrite the data.The elastic exchange magnet?ES?made by the interface exchange function can be used to increase the magnetic energy level?BH?max of NdFeB magnets,and can also be used to reduce the H_c of L1₀-FePt.The exchange elastic magnet is composed of two kinds of materials:hard magnet?HM?and soft magnet?SM?,accompanied by exchange coupling at the interface of the two phases.The combination of the high residual magnetic flux density?Br?of HM and the high residual magnetization?Ms?of SM can effectively reduce the H_c of HM.The inverted magnetic domain in the ES is generated in the SM phase,and the domain wall can enter the hard magnetic phase through the interface under the action of a lower magnetic field,thereby reducing the switching field of the hard magnetic phase.The shape of the magnetization curve mainly depends on the thickness of the soft magnetic phase.Some researchers have thought about the FePt/Fe double-layer film,but Fe is too easy to oxidize,and the crystal structure and lattice constant of the two materials are different,the interface distortion is obvious,and the interface extension is poor,which affects the characteristics.The best solution to this problem is to form a heterojunction,which can be achieved using the L1₀-Fe Pt/A1-FePt structure.Using a Si?001?substrate heated to 100? as a substrate,sputtering a 50 nm FePt film,setting different temperatures for heat treatment,analyzing its structure and magnetic changes,looking for better formation of L1₀-FePt/A1-FePt The condition of the junction.However,diffusion between Si and FePt is easy to occur.Therefore,an MgO isolation layer is inserted between Si and FePt.After growing a 10 nm thick MgO layer,raise the temperature to 400?,and alternately grow(FePt/MgO multilayer film or(?FePt+MgO?/MgO splash/alternate multilayer film.After heat treatment at different temperatures,analysis Its structure and magnetic changes.The main results are as follows:1.Sputtering 50 nm Fe Pt thin film directly on Si?001?substrate.After the heat treatment temperature T_a is kept in the range of[400,600]?for 2 hours,the coercive force of H_c does not change much.Maximum at T_a=500??magnetized in the in-plane direction,5.45 kOe;magnetized in the direction perpendicular to the film surface,3.48 kOe?.When the heat treatment temperature is raised again,an uncalibrated peak appears,indicating that the interface between the Si substrate and the FePt alloy has undergone qualitative change.2.The MgO isolation layer is inserted between the Si?001?substrate and FePt?50nm?,the heat resistance of the film is greatly improved,and the original shape can be maintained at T_a=600?,but more More FePt will be converted into L1₀ phase.This shows that using the MgO layer to isolate the film and the base can effectively prevent the diffusion between the film and the substrate.3.On a Si?001?single crystal substrate heated to 100?,grow a 10 nm thick MgO film by magnetron sputtering,adjust the temperature to 400?,and alternately sputter FePt/MgO or sputter Fe Pt+MgO After that,MgO is sputtered to obtain an alternately grown multilayer structure.By heat treatment at different temperatures,the film can achieve different degrees of A1?L1₀ transition,and the exchange elasticity contained in it is analyzed.?1?FePt/MgO alternately grows,because MgO isolates the particles between the Fe Pt layers,blocking the coupling effect between the magnetic particles in the vertical direction,making the easy axis direction in-plane.Because the thickness of each layer of FePt is thin enough and is affected by the interlayer isolation of MgO,the hysteresis loop has no shoulders,that is,the size of the soft magnetic phase does not exceed the exchange length.By changing the thickness of the MgO layer,the proportion of the A1 phase?L1₀ phase can be adjusted,and all have high heat resistance.?2?In the?FePt+MgO?/MgO system,MgO in the co-sputtered layer is embedded between FePt particles,which further weakens the exchange coupling between FePt particles.The phase L1₀ and phase A1 coexist in FePt particles,forming an exchange-coupling complex.Since the exchange magnets are separated from each other by MgO,the coupling effect between the particles is weakened,and the soft magnetic phase is only constrained by the nearest neighbor hard magnetic phase,and the coercive force will be reduced.As long as a small amount of non-magnetic substance MgO is incorporated in the co-sputtered layer,the coercive force can be reduced by nearly half.?3?By changing the thickness of the FePt+MgO co-sputtered layer,the magnetic properties can be further adjusted.The way of embedding MgO in the layer provides a new way to adjust the coercivity of FePt.