Multiple Magnetization Reversal Channels Observed in a 3d-4f Single Molecule Magnet

Asma Amjad,Albert Figuerola,Lorenzo Sorace,Andrea Caneschi

doi:10.3390/magnetochemistry2020027

Abstract

The present study discusses the magnetic dynamics of a previously reported cyanide bridged 3d-4f dinuclear DyIIICoIII complex. Following the axial anisotropy suggested by previous Electron Paramagnetic Resonance spectroscopy (EPR) analysis, the complex turned out to show slow relaxation of the magnetization at cryogenic temperature, and this was studied in different temperature and field regimes. The existence of multichannel relaxation pathways that reverse the magnetization was clearly disclosed: a tentative analysis suggested that these channels can be triggered and controlled as a function of applied static magnetic field and temperature. Persistent evidence of a temperature independent process even at higher fields, attributable to quantum tunneling, is discussed, while the temperature dependent dynamics is apparently governed by an Orbach process. The broad distribution of relaxation rates evidenced by the ac susceptibility measurements suggest a relevant role of the intermolecular interactions in this system.

Highlights

Many interdisciplinary efforts are underway to comprehend the magnetic behavior of lanthanide based molecular magnets (MMs); this has proven to be a complex and tangled task owing to the large orbital contribution of lanthanides, along with weak exchange interactions and significant crystal field effects normally occurring in such systems [1,2,3,4,5]
The objective of these dedicated attempts is to individually identify and explain the contribution of the aforementioned processes to the static and dynamic magnetic properties of the lanthanide based molecules. Many of these attempts have been performed in mixed d-f metal ion complexes, as a way to bypass the weakness of the f-f magnetic exchange interactions
These mixed d-f complexes allow the use of the so-called diamagnetic substitution approach, where the transition paramagnetic ion exchange-coupled to the lanthanide ion is substituted with a diamagnetic analogue, at the same time keeping the integrity of the crystal structure

Summary

Introduction

Many interdisciplinary efforts are underway to comprehend the magnetic behavior of lanthanide based molecular magnets (MMs); this has proven to be a complex and tangled task owing to the large orbital contribution of lanthanides (large magnetic anisotropy), along with weak exchange interactions and significant crystal field effects normally occurring in such systems [1,2,3,4,5]. More recently, a lot of success has been achieved in understanding the key factors affecting the processes leading to slow relaxation of the magnetization in lanthanide based MMs—much more ubiquitous than initially thought—by use of multiple techniques, including magnetometry, susceptibility, Electron Paramagnetic Resonance spectroscopy (EPR), luminescence and magnetic circular dichroism [8,9,10,11], often coupled to detailed ab initio calculations This provided aMnadgnmetoachgenmeisttircy c2i0r1c6u, 2l,a2r7dichroism [8,9,10,11], often coupled to detailed ab initio calculations. This prov2idofe1d0 breakthroughs in the understanding of the role of the magnetic anisotropy and the crystal field effects ibnredaekttehrrmouingihnsginhitghhe ubnadrreiresrtsantoditnhgeorfetlhaxeartoiolenoof fthme amgangentieztaictioanni,saontrdoppyroavniddethde kceryystianlpfiuetlsdfeofrfetchtes dinesdiegtneramnidnisnygnhthigehsibsaorfriceorsmtopothuenrdeslasxhaotiwoninogf rmelaagtniveetliyzahtiiognh, amnadgpnreotviziadteidonkebyloicnkpiuntgs ftoemr tpheerdaetusirgens [a1n2d–1s4y]n. tIhnetshiissoffracmomewpoourkn,ditsisshinowterinesgtirneglattoivneolytehtihgaht mmoagstnoeftitzhaetisoynstbelmocskeianrglietermsypnetrhaetsuirzeesd[1fo2r–1th4e]. sIntutdhyisofrfatmheeiwr ostrakt,icit misaingtneerteisctipnrgoptoerntoietes thhaavtemnoostt yoef tthbeeesynsctehmarsaecaterrliiezredsyfnotrhethsiezeddynfoarmthicessotuf dthyeoirf mthaeigrnsetatitzicatmioang,ndeetsicppitreotpheertfieews heaxvceepntoitoynesttbheaetnhcahvaerpacrtoevriizdeeddfcolreathreedviydneanmceicosfotfhtehierirpmotaegnntieatliiztiaetsioinn, tdheissprietegathrde f[e1w5,1e6x]c.eptions that have provided clear evidence of their potentialities in this regard [15,16]

Methods

Results

Conclusion