Magnetic systems at criticality: different signatures of scaling

Different aspects of critical behaviour of magnetic materials are presented and discussed. The scaling ideas are shown to arise in the context of purely magnetic properties as well as in that of thermal properties as demonstrated by magnetocaloric effect or combined scaling of excess entropy and order parameter. Two non-standard approaches to scaling phenomena are described. The presented concepts are exemplified by experimental data gathered on four representatives of molecular magnets.Comment: 33 pages, 16 figure

Magnetization dynamics and coherent spin manipulation of a propeller Gd(III) complex with the smallest helicene ligand

A homoleptic gadolinium(III) complex with the smallest helicene-type ligand, 1,10-phenanthroline-N,N'-dioxide (phendo) [Gd(phendo)(4)](NO3)(3)center dot xMeOH (phendo = 1,10-phenanthroline-N,N'-dioxide, MeOH = methanol), shows slow relaxation of the magnetization characteristic for Single Ion Magnets (SIM), despite negligible magnetic anisotropy, confirmed by ab initio calculations. Solid state dilution magnetic and EPR studies reveal that the magnetization dynamics of the [Gd(phendo)(4)](3+) cation is controlled mainly by a Raman process. Pulsed EPR experiments demonstrate long phase memory times (up to 2.7 mu s at 5 K), enabling the detection of Rabi oscillations at 20 K, which confirms coherent control of its spin state.</p

Enforcing Multifunctionality: A Pressure-Induced Spin-Crossover Photomagnet

Photomagnetic compounds are usually achieved by assembling preorganized individual molecules into rationally designed molecular architectures via the bottom-up approach. Here we show that a magnetic response to light can also be enforced in a nonphotomagnetic compound by applying mechanical stress. The nonphotomagnetic cyano-bridged Fe^II–Nb^IV coordination polymer {[Fe^II(pyrazole)₄]₂[Nb^IV(CN)₈]·4H₂O}_<i>n</i> (<b>FeNb</b>) has been subjected to high-pressure structural, magnetic and photomagnetic studies at low temperature, which revealed a wide spectrum of pressure-related functionalities including the light-induced magnetization. The multifunctionality of <b>FeNb</b> is compared with a simple structural and magnetic pressure response of its analog {[Mn^II(pyrazole)₄]₂[Nb^IV(CN)₈]·4H₂O}_<i>n</i> (<b>MnNb</b>). The <b>FeNb</b> coordination polymer is the first pressure-induced spin-crossover photomagnet

Molecular alloying drives valence change in a van der Waals antiferromagnet

\ua9 2025 Elsevier Inc. Bespoke van der Waals (vdW) crystals provide command over the confinement and transport of charge, spin, and heat within and between two-dimensional (2D) layers. We report a novel functionality in vdW crystals by actuating valence changes through molecular alloying. The net materials Cr(pyrazine)2Br2 and Cr(pyrazine)2I2 are aliovalent, hosting Cr(III) and Cr(II), respectively, due to disparate crystal field potentials. Pressurizing and thereby strengthening of the crystal field compresses the Cr(pyrazine)2I2 layers significantly, but no Cr valence change is induced. However, alloyed Cr(pyrazine)2I2−xBrx phases exhibit hysteretic and tunable Cr(II) ⇄ Cr(III) interconversions with concomitant charge injection into the net. The valence switch manifests drastic changes to the magnetization and the electrical conductivity, which varies by up to five orders of magnitude during the valence conversion. This use of coordination chemistry addresses a gap in vdW and 2D materials science, where electronic structure engineering via valence change events has remained elusive