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Graphdiyne (GDY) was prepared by a cross-coupling reaction and its magnetic properties were studied. The results show that the as-prepared GDY is spin-half paramagnetism. GDY shows the increase in the spin density by annealing, and antiferromagnetism appears after annealing at 600°C. The density functional calculations show that (i) the hydroxyl groups on the chain of GDY sheet are the major magnetic sources, and (ii) these hydroxyl groups have the high barrier energy of 1.73 eV for migrating from the ring site to chain site, which can prevent the hydroxyl groups’ clustering and may favor the antiferromagnetism in the annealed GDY. [ABSTRACT FROM AUTHOR]

A giant magnetocaloric effect has been observed around the Curie temperature, TC∼42 K, in NdMn1.7Cr0.3Si2 with no discernible thermal and magnetic hysteresis losses. Below 400 K, three magnetic phase transitions take place around 380 K, 320K and 42 K. Detailed high resolution synchrotron and neutron powder diffraction (10-400 K) confirmed the magnetic transitions and phases as follows: TN intra∼380K denotes the transition from paramagnetism to intralayer antiferromagnetism (AFl), TN inter∼320K represents the transition from the AFl structure to the canted antiferromagnetic spin structure (AFmc), while TC∼42K denotes the first order magnetic transition from AFmc to canted ferromagnetism (Fmc+F(Nd)) due to ordering of the Mn and Nd sub-lattices. The maximum values of the magnetic entropy change and the adiabatic temperature change, around TC for a field change of 5 T are evaluated to be -ΔSM max∼15.9 J kg-1 K-1 and ΔTad max∼5K, respectively. The first order magnetic transition associated with the low levels of hysteresis losses (thermal <∼0.8 K; magnetic field <∼0.1 T) in NdMn1.7Cr0.3Si2 offers potential as a candidate for magnetic refrigerator applications in the temperature region below 45 K [ABSTRACT FROM AUTHOR]

We present a spectromicroscopy study of the two distinct metal-insulator transitions in (V1-xCrx)2O3, x = 0.011. The coexistence of metallic and insulating domains was observed with scanning photoelectron microscopy for both the paramagnetic insulator-paramagnetic metal and paramagnetic metal-antiferromagnetic insulator transitions, evidencing a clear correlation between their nucleation regions. Although these two transitions are very different in nature and underlying mechanism, in both cases the morphology of their phase separation is influenced by structural inhomogeneities. These results demonstrate the general relevance of strain caused by local lattice distortions in guiding the intrinsic tendency towards phase separation in Mott materials. [ABSTRACT FROM AUTHOR]

The lattice and electronic and magnetic transport properties of the antiperovskite structure Mn3Zn1-xGexN compounds were investigated. For Mn3ZnN, there is a magnetic transition from antiferromagnetic to paramagnetic near 185 K. Correspondingly, the resistivity shows an abrupt drop, but any sudden change of lattice parameters is not found. However, it is interesting that the partial substitution of Ge for Zn induces a lattice contraction near the magnetic transition temperature, where a drop of the resistivity remain, and the transition temperature point increases and the temperature range is broadened with increasing doped Ge contents. The thermodynamics properties were also investigated. [ABSTRACT FROM AUTHOR]

The authors demonstrate that nanometer size ZnMnO nanopowders, grown from zinc and manganese (II) acetates at low temperatures under microwave radiation, are free of Mn clusters and the inclusion of Mn oxides. These nanopowders show a strong paramagnetic phase with only a weak antiferromagnetic contribution due to Mn–Mn interactions. [ABSTRACT FROM AUTHOR]

A 0.5% Al-doped Zn0.895Co0.100O polycrystalline powder was synthesized by the co-precipitation method. Raman spectroscopy revealed that divalent cobalt ions were substituted for Zn2+ ions into the ZnO matrix and that Al ions activate additional modes which are nonspecific to the dopant. These additional modes disappear after annealing at 1373 K for 1 h under Ar flow. We suggest that the electrical dopant becomes active in substitutional sites after annealing. Resistance measurements confirm that free carriers were created in our sample. Nevertheless, the sample shows the same magnetic properties: a mixture of paramagnetism and antiferromagnetism. [ABSTRACT FROM AUTHOR]

Magnetic transitions and magnetoresistance of the HfFe[SUB6]Ge[SUB6]-type Y[SUB0.5]Ho[SUB0.5]Mn[SUB6]Sn[SUB6] compound have been investigated in the temperature range of 5-380 K. It was found that the compound displays paramagnetism, ferrimagnetism, antiferromagnetism, and reentrant ferrimagnetism with decreasing temperature. The temperature range of the antiferromagnetic state can be narrowed by increasing the magnetic field, and the metamagnetic transition from the antiferro- to ferrimagnetic state can be induced by a fairly small threshold field (<6 kOe). The antiferro-ferrimagnetic transition is accompanied by a large magnetoresistance effect of about - 16% at 100 K. The magnetic transitions with temperature and magnetic field are both of the second order. [ABSTRACT FROM AUTHOR]

The magnetization of Ga[sub 1-x]Mn[sub x]N (x<0.1) crystals was measured as a function of the magnetic field and temperature. Paramagnetic behavior typical of spin S=5/2 expected for Mn[sup 2+] (d[sup 5]) magnetic centers was observed in the temperature range of 2 K