structural and magnetic properties
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2022 ◽  
Vol 12 (2) ◽  
pp. 695
Alessandra Geddo Lehmann ◽  
Giuseppe Muscas ◽  
Maurizio Ferretti ◽  
Emanuela Pusceddu ◽  
Davide Peddis ◽  

We investigated the structural and magnetic properties of 20 nm-sized nanoparticles of the half-doped manganite Ho0.5Ca0.5MnO3 prepared by sol-gel approach. Neutron powder diffraction patterns show Pbnm orthorhombic symmetry for 10 K < T < 290 K, with lattice parameters a, b, and c in the relationship c/√2 < a < b, indicating a cooperative Jahn–Teller effect, i.e., orbital ordering OO, from below room temperature. In contrast with the bulk samples, in the interval 250 < T < 300 K, the fingerprint of charge ordering (CO) does not manifest itself in the temperature dependence of lattice parameters. However, there are signs of CO in the temperature dependence of magnetization. Accordingly, below 100 K superlattice magnetic Bragg reflections arise, which are consistent with an antiferromagnetic phase strictly related to the bulk Mn ordering of a charge exchange-type (CE-type), but characterized by an increased fraction of ferromagnetic couplings between manganese species themselves. Our results show that in this narrow band half-doped manganite, size reduction only modifies the balance between the Anderson superexchange and Zener double exchange interactions, without destabilizing an overall very robust antiferromagnetic state.

2022 ◽  
Vol 8 (1) ◽  
pp. 8
Komala Pandurangan ◽  
Anthony B. Carter ◽  
Paulo N. Martinho ◽  
Brendan Gildea ◽  
Tibebe Lemma ◽  

Structural and magnetic properties of a new spin crossover complex [Mn(4,6-diOMe-sal2323)]+ in lattices with ClO4−, (1), NO3−, (2), BF4−, (3), CF3SO3−, (4), and Cl− (5) counterions are reported. Comparison with the magnetostructural properties of the C6, C12, C18 and C22 alkylated analogues of the ClO4− salt of [Mn(4,6-diOMe-sal2323)]+ demonstrates that alkylation effectively switches off the thermal spin crossover pathway and the amphiphilic complexes are all high spin. The spin crossover quenching in the amphiphiles is further probed by magnetic, structural and Raman spectroscopic studies of the PF6− salts of the C6, C12 and C18 complexes of a related complex [Mn(3-OMe-sal2323)]+ which confirm a preference for the high spin state in all cases. Structural analysis is used to rationalize the choice of the spin quintet form in the seven amphiphilic complexes and to highlight the non-accessibility of the smaller spin triplet form of the ion more generally in dilute environments. We suggest that lattice pressure is a requirement to stabilize the spin triplet form of Mn3+ as the low spin form is not known to exist in solution.

2021 ◽  
Vol 413 ◽  
pp. 65-73
Bouziane Mamar ◽  
Bergheul Said ◽  
Renane Rachid

In this paper, a theoretical model based on multi-gene genetic programming (MGGP) approach has been applied to predict the structural and magnetic properties in nanocrystalline Fe–Ni powders prepared by mechanical alloying (MA) using a planetary ball mill. The MGGP model was used to correlate the input parameters (milling speed, chemical composition, and milling time), to output parameters (crystallite size and coercivity) of nanocrystalline Fe–Ni powders. The model obtained was tested with additional data to demonstrate its performance and prediction ability. The MGGP model is a robust and efficient method to find an accurate mathematical relationship between input and output data. A sensitivity analysis study was applied to determine the most influential milling parameters on the crystallite size and coercivity.

T. V. Drokina ◽  
D. A. Velikanov ◽  
O. A. Bayukov ◽  
M. S. Molokeev ◽  
G. A. Petrakovskii

2021 ◽  
Vol 128 (1) ◽  
K. Subrahmanya Sarma ◽  
Ch. Rambabu ◽  
G. Vishnu Priya ◽  
M. K. Raju ◽  
D. Parajuli ◽  

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