Related Experiment Video
Updated: Aug 22, 2026
Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Diamagnetic to Cluster Glass Transition in the Mn-Substituted δ-Co2.5Zn17.5 Chiral Intermetallic Phase
Rahul Pan1, Riju Dey2, Amit Mondal1
1Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur721302, India.
None:
This study focuses on the binary δ-Co2.5Zn17.5 and pseudobinary δ-Co2.5-xMnxZn17.5 (x = 0-1.2) intermetallic phases, prepared via a high-temperature synthetic route. The crystal structure and atomic distribution of δ-Co2Mn0.5Zn17.5 were established using X-ray and neutron diffraction experiments. The pseudobinary δ-Co2Mn0.5Zn17.5 adopts a chiral crystal structure (P64), consistent with the binary δ-Co2.5Zn17.5. Theoretical calculations were employed to understand the site preferences of Co and Zn, as well as the overall phase stability of the binary compound. Interestingly, the substitution of Mn for Co occurs through Zn mediation (an indirect substitution). In the crystal structure, Mn occupies Zn sites at the 6c position; the displaced Zn then occupies the 3a site, ultimately maintaining the stoichiometry of Co2Mn0.5Zn17.5. The binary δ-Co2.5Zn17.5 exhibits diamagnetism, whereas Mn incorporation into the binary δ-Co2.5Zn17.5 induces cluster-glass magnetism in the pseudobinary δ-Co2Mn0.5Zn17.5, with a spin-freezing temperature of 10 K. While both compounds are structurally chiral, this chirality does not appear to influence their magnetic behavior. Instead, the cluster-glass state in the Mn-substituted phase is driven by the atomic randomness of the Mn atoms in the structural lattice. This out-of-equilibrium behavior below 10 K is further supported by the alternating-current (ac) magnetic susceptibility, thermoremanent magnetization, and the thermal memory effect.
Related Concept Videos
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:42Valence Bond Theory
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:52Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
01:26Diamagnetism
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
02:33Phase Transitions: Sublimation and Deposition