Molecular magnetism

During the past two decades single molecule magnets (SMMs) have attracted much attention due to the fascinating properties such as quantum tunneling of magnetization (QTM) or quantum phase interference making them potential candidates for future applications as basic units in information technology devices. The Mn12 family ([Mn12O12(O2CL)16(H2O)4] with L – various ligands) with a S = 10 ground state represents the first discovered and to date best investigated class. Up to now, a huge number of different molecules that show magnetic anisotropy were synthesized and investigated on the border between chemistry and physics. By tailoring the ligand shell it is possible to control magnetic, mechanical, optical and electrical properties to meet a broad variety of requirements for possible applications. Beside the Mn12 family, Fe4-complexes and rare earth complexes are just few of a number of interesting candidates which open a door to fascinating research topics, of fundamental as well as of technological interest.

Our research is focused on the investigation of individual SMM molecules and SMM monolayers on surfaces. The ligand shell of SMM complexes is optimized for the deposition on (semi)-conductive surfaces and for the investigation by means of scanning tunneling microscopy (STM, see Figure below). The structure of the obtained complexes is characterized by means of X-ray diffraction, and SQUID-measurements confirm the presence of the expected magnetic properties with a typical step-wise hysteresis loop (see Figure below). A non-destructive deposition method even for fragile compounds was home-built by using the electrospray ionization technique. To gain insight into magnetic properties of previously characterized, clean SMM monolayers on surfaces we employ X-ray magnetic circular dichroism (XMCD) measurements (see Figure below).