Magnetic, structural and Mössbauer study of soils from an ancient mining area in Huancavelica-Peru

We present the magnetic, structural and 57Fe Mossbauer characterization of soils collected from an ancient mercury contaminated city named Huancavelica in Peru. The characterization results indicate that silicates and carbonates are the main mineralogical constituents in the samples. In addition, 57Fe Mössbauer spectra at room temperature reveal, the presence of two components: a magnetic component related to magnetic Fe-oxides (magnetite, hematite, goethite) and a high non-magnetic component related to Fe+3 in high spin configuration and tetrahedral coordination in silicates. The magnetization measurements present screening of paramagnetic, ferromagnetic and antiferromagnetic signals, typical from soils containing different silicates and iron minerals. Remarkably the Verwey and Morin transitions corresponding to magnetite and hematite, respectively, are screened by the paramagnetic signal corresponding to the major silicate components in the samples. Overall, the soils are mainly composed of crystalline and amorphous silicates, calcites and iron bearing which are typical from Andean soils.

Magnetic structure study of the sawtooth chain antiferromagnet $$\hbox {Fe}_2\hbox {Se}_2\hbox {O}_7$$

A magnetic structure of the sawtooth-chain antiferromagnet $$\hbox {Fe}_2\hbox {Se}_2\hbox {O}_7$$ Fe 2 Se 2 O 7 was investigated by magnetization measurements, single crystalline and powder neutron diffraction experiments, and a further analysis on the Mössbauer spectra. These experiments revealed a nearly collinear antiferromagnetic structure with magnetic moments aligned along the b-axis, indicating dominant antiferromagnetic exchanges between Fe(1)–Fe(2) and Fe(2)–Fe(3) sites. The magnon dispersion relation derived from the linear spin wave approximation suggests the possible flat band nature of magnons.

Will Magnetic Properties near Pressure Induced Quantum Critical Phenomena Be Elucidated?

Hiraoka et al. developed an opposed anvil-type pressure cell for magnetization measurements which combines a large sample space and is capable of generating higher pressures up to 6.3 GPa.