| The advances of information technology have accelerated the miniaturization of information storage and transport devices.The next-generation spintronics devices in the future will be built on single-molecule magnets(SMMs),because SMMs usually exhibit a series of advantages as follows.(ⅰ)They are composed of only tens of atoms,with the size scale of 1 nm.This feature fulfills the miniaturization of devices.(ⅱ)There are abundant kinds of SMMs with rich magnetic properties depending on the transition metal atoms in SMMs.(ⅲ)The electronic and magnetic states can be engineered conveniently.In this dissertation,we studied the electronic,magnetic and transport properties of two kinds of SMMs,based on first-principles calculations.The main results are summarized in the following:(1)We calculated the magnetic anisotropy energie(MAE)of transition metal dithiolene[TM(MNT)2]molecules and found that the largest MAE is only 4 meV.Interestingly,the MAE can be significantly enhanced when an additional transition metal adatom is placed on the TM(MNT)2 molecule.In particular,the MAE of Os-Os(MNT)2 is 47 meV and that of Os-Ir(MNT)2 is 52 meV.Such giant MAE ensure the stability of the spin orientation of the corresponding SMMs above the room temperature,which is promising for practical application in spintronics devices.(2)We studied the transport property of Salophen molecular chain.We built the Salophen chain with two Salophen molecules,and then put it between two Au electrodes,forming a single-molecule magnetic junction(SMMJ).When the spins of the two Salophen molecules are ferromagnetic,the SMMJ is on,i.e.the electric current can pass through the SMMJ.In addition,the current is almost completely spin-polarized.On the contrary,when the two Salophen molecules couple with each other antiferromagnetically,the SMMJ is off,i.e.the electric current is blocked and cannot pass through the SMMJ.Therefore,such an SMMJ is of potential application in quantum switch and molecular spin valve. |
