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Register a new userAn overview of the structural correlation of magnetic and electrical properties of Pr2NiMnO6 Double perovskite
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Double perovskites R2NiMnO6 (R= Rare earth element) (RNMO) are a significant class of materials owing to their varied tunability of the magnetic and electrical properties with the structural modifications. Pr2NiMnO6 (PNMO) is one of the least explored members of this series, which shows spin-phonon coupling, magnetocaloric effect, and electrochemical performance for various applications such as spintronics, magnetocaloric refrigerant, and solid oxide fuel cells. Most of the studies in PNMO are limited to the application domain and focus on the comparative study with different rare earth elements. Detailed structural studies like neutron diffraction are sparse in PNMO samples which will give a perception to the ordering in the compound that strongly depends on the physical and chemical properties. This review article goes through the various aspects of PNMO materials that have been reported till now and showcase the octahedral distortions and corresponding structural changes and the exchange interactions, which in turn correlates with the magnetic and electrical properties. The comparison study of PNMO with other members of the RNMO family and the relevance of PNMO over other members is also tried to showcase through this article. Hope this article provides an insight into the scope of studies in PNMO material for exploring unexposed properties of the materials in the double perovskite family.
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Rare earth perovskite cobaltites are increasingly recognized as materials of importance due to rich physics and chemistry in their ordered-disordered structure for the same composition. Apart from colossal magnetoresistance effect, like manganites, the different forms of cobaltites exhibit interesting phenomena including spin, charge and orbital ordering, electronic phase separation, insulator-metal transition, large thermoelectric power at low temperature. Moreover, the cobaltites which display colossal magnetoresistance effect could be used as read heads in magnetic data storage and also in other applications depending upon their particular properties. The A-site ordereddisordered cobaltites exhibit ferromagnetism and metal-insulator transitions as well as other properties depending on the composition, size of A-site cations and various external factors such as pressure, temperature, magnetic field etc. Ordered cobaltites, having a 112-type layered structure, are also reported to have an effectively stronger electron coupling due to layered A-site cationic ordering. Most importantly for the present article we focus on La-Ba-Co-O based ordered-disordered perovskite phases, which exhibit interesting magnetic and electron transport properties with ferromagnetic transition, TC ~ 177K, and it being the first member of lanthanide series. Zener double exchange mechanism considered to be crucial for understanding basic physics of the ferromagneticmetallic phase, yet does not explain clearly the insulating-type phase. In terms of electron transport the ferromagnetic-metallic or insulating/semiconducting states have been discussed in the present article with different types of hopping model.
Nanocrystalline ribbons of inverse Heusler alloy Mn2Ni1.6Sn0.4 have been synthesised by melt spinning of the arc melted bulk precursor. The single phase ribbons crystallize into a cubic structure and exhibit very fine crystallite size of < 2 nm. Temperature dependent magnetization (M-T) measurements reveal that austenite (A)-martensite (M) phase transition begins at T~248 K and finishes at T~238 K during cooling cycle and these values increase to T~267 K and T~259 K while warming. In cooling cycle, the A-phase shows ferromagnetic (FM) ordering with a Curie temperature T~267 K, while both the FM-antiferromagnetic (AFM) and M-transitions occur at T~242 K. The M-phase undergoes FM transition at T~145 K. These transitions are also confirmed by temperature dependent resistivity measurements. The observed hysteretic behaviour of magnetization and resistivity in the temperature regime spanned by the A-M transition is a manifestation of the first order phase transition. Magnetization and susceptibility data also provide unambiguous evidence in favour of spin glass . The scaling of the glass freezing temperature (Tf) with frequency, extracted from the frequency dependent AC susceptibility measurements, confirms the existence of canonical spin glass at T<145 K. The occurrence of canonical spin glass has been explained in terms of the nanostructuring modified interactions between the FM correlations in the martensitic phase and the coexisting AFM.
Density functional theory (DFT) calculations are performed to predict the structural, electronic and magnetic properties of electrically neutral or charged few-atomic-layer (AL) oxides whose parent systems are based on polar perovskite $KTaO_{3}$. Their properties vary greatly with the number of ALs ($n_{AL}$) and the stoichiometric ratio. In the few-AL limit ($n_{AL}leqslant 14$), the even AL (EL) systems with chemical formula $(KTaO_{3})_{n}$ are semiconductors, while the odd AL (OL) systems with formula ($K_{n+1}Ta_{n}O_{3n+1}$ or $K_{n}Ta_{n+1}O_{3n+2}$) are half-metal except for the unique $KTa_{2}O_{5}$ case which is a semiconductor due to the large Peierls distortions. After reaching certain critical thickness ($n_{AL}>14$), the EL systems show ferromagnetic surface states, while ferromagnetism disappears in the OL systems. These predictions from fundamental complexity of polar perovskite when approaching the two-dimensional (2D) limit may be helpful for interpreting experimental observations later.
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Using density-functional theory calculations, we investigated the electronic structure and magnetic exchange interactions of the ordered 3d-5d double perovskite Sr2FeOsO6, which has recently drawn attention for interesting antiferromagnetic transitions. Our study reveals the vital role played by long-range magnetic exchange interactions in this compound. The competition between the ferromagnetic nearest neighbor Os-O-Fe interaction and antiferromagnetic next nearest neighbor Os-O-Fe-O-Os interaction induces strong frustration in this system, which explains the lattice distortion and magnetic phase transitions observed in experiments.
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