Single-Ion Magnets with Giant Magnetic Anisotropy and Zero-Field Splitting

Abstract

The design of mononuclear molecular nanomagnets exhibiting a huge energy barrier to the reversal of magnetization have seen a surge of interest during the last few decades due to their potential technological applications. More specifically, singleion magnets are peculiarly attractive by virtue of their rich quantum behavior and distinct fine structure. These are viable candidates for implementation as single-molecule high-density information storage devices and other applications in future quantum technologies. The present review presents the comprehensive state of the art in the topic of single-ion magnets possessing an eminent magnetization-reversal barrier, very slow magnetic relaxation and high blocking temperature. We turn our attention to the achievements in the synthesis of 3d and 4f single-ion magnets during the last two decades and discuss the observed magnetostructural properties underlying the anisotropy behavior and the ensuing remanence. Furthermore, we highlight the fundamental theoretical aspects to shed light on the complex behavior of these nanosized magnetic entities. In particular, we focus on key notions, such as zero-field splitting, anisotropy energy and quantum tunneling of the magnetization and their interdependence.

Field-induced magnetic relaxation in heteropolynuclear LnIII/ZnII metal organic frameworks: cerium and dysprosium cases

“…6. The curves fit perfectly to a Raman-like decay process with C = 10 2.8 (2) , m = 2.6(3) and C = 10 2.7 (2) , m = 2.7(4) under 1 kOe and 2 kOe external fields, respectively. Although a value of m = 9 would be expected, several examples of lower values (m E 4-5) have also been reported for Kramer ions.…”

“…In subsequent years, several studies have shown that many lanthanide complexes can also show magnetization relaxation, some at much higher temperatures than those originally reported by Ishikawa. 2 For example, the dysprosium metallocene cation [Dy(Cp ttt ) 2 ] + (Cp ttt = 1,2,4tri(tert-butyl)cyclopentadienide) behaves as a single ion magnet with a magnetization reversal barrier U eff higher than 1250 cm À1 in zero field and a magnetic blocking temperature T B = 60 K, below which it exhibits hysteresis and coercivity. 3,4 Furthermore, changing Cp ttt by Cp iPr5 and Cp* (penta-isopropylcyclopentadienide and pentamethylcyclopentadienide, respectively) in [(Cp iPr5 )Dy(Cp*)] + made it possible for the first time to overcome the nitrogen boiling point barrier with T B = 80 K and U eff = 1541 cm À1 .…”

Magnetic Behavior of Trigonal (Bi-)pyramidal 3d8 Mononuclear Nanomagnets: The Case of [Ni(MDABCO)2Cl3]ClO4

“…Describing the magnetic properties of the complex [Ni-(MDABCO) 2 Cl 3 ] +37 only within the conventional analytic techniques and approximations 11,25,38,47 turns out to be unfeasible as we have shown here. The energy spectrum of the compound obtained within these approaches is depicted in Figure 2 with the corresponding numerical representation given in the Supporting Material (Section S.5).…”

“…The magnetic properties of transition-metal-based molecular and single-ion magnets are tightly related to the local coordination of metal ions. In general, the CF environment shaped by the bond lengths, type of ligands, coordination number, and geometric symmetry is the main precursor to a particular fine structure related to the ground state (FSG) resulting from the spin–orbit (SO) coupling. ,− There exists, however, an additional characteristic behind the distinct magnetic behavior among the metal ions belonging to the same row of the periodic system of elements, that is, the extent of valence subshell occupancy influencing quantitatively the effect of CF and SO coupling on the fine structure (FS) due to Pauli’s principle. In that respect, the high-spin 3d 8 coordination complexes and their ensuing polynuclear nanomagnets − are of particular interest, since at a given coordination, they tend to show an unusual magnetic anisotropy (MA).…”

Spectroscopic techniques to probe magnetic anisotropy and spin–phonon coupling in metal complexes

“…For lanthanide-based SMMs, there are also barriers for magnetization and relaxation processes. [3][4][5][6][7]11,[13][14][15][16][17][18][19][21][22][23][24][25]36 Recent advancements have contributed to the development of more efficient SMMs with improved stability and control over magnetic behavior.…”