Magnetic-field induced melting of long-range magnetic order akin to Kitaev insulators in the metallic compound TbSi.

There have been constant efforts to find 'exotic' quantum spin-liquid (QSL) materials. Some of the transition metal insulators dominated by the direction-dependent anisotropic exchange interaction ('Kitaev model' for honeycomb network of magnetic ions) are considered to be promising cases for the same. In such Kitaev insulators, QSL is achieved from the zero-field antiferromagnetic state by the application of magnetic-field, suppressing other exchange interactions responsible for magnetic order.

Insight into the negative magnetization and anomalous exchange-bias in DyFe5Al7 through neutron depolarization and neutron diffraction studies.

We have provided the mesoscopic and microscopic understandings of polarity reversal of the magnetization or negative magnetization (NM) below TCOMP = 93 K in an exotic magnetic material containing three magnetic sublattices, viz., DyFe5Al7 crystallizing in ThMn12 structure, using neutron depolarization and neutron diffraction techniques. A full recovery of the neutron beam polarization at the TCOMP in a neutron depolarization experiment reveals a total compensation of magnetization inside the magnetic domains in the sample.

Destruction of multiferroicity in TbBaNiO by Sr-doping and its implication to magnetodielectric coupling.

The Haldane spin-chain compound, TbBaNiO, with two antiferromagnetic transitions, one at T   =  63 K and the other at T   =  25 K, has been recently shown to be an exotic multiferroic below T . Here, we report the results of our investigation of Sr doping at the Ba site by magnetization, heat-capacity, magnetodielectric (MDE) and pyrocurrent measurements. An intriguing finding, which we stress, is that the ferroelectricity is lost even for a doping level of ten atomic percent, though magnetic ordering prevails.

Observation of magnetoelastic and magnetoelectric coupling in Sc doped BaFeO due to spin-glass-like phase.

The present work reports magnetic, magnetoelastic and magnetoelectric (ME) response of scandium (Sc) doped barium hexaferrite, BaFeScO. DC magnetization shows that partial substitution of non-magnetic Sc for Fe in barium hexaferrite results in a reduction of Curie temperature (T ) from 730 K known for the parent compound BaFeO to 430 K. Magnetization measurements show that, in BaFeScO, in addition to the magnetic transition at 250 K corresponding to longitudinal conical magnetic structure, another magnetic anomaly occurs in the vicinity of 50 K (T ).

Magnetic behavior of metallic kagome lattices, TbRuAl and ErRuAl.

We report the magnetic behavior of two intermetallic-based kagome lattices, TbRuAl and ErRuAl, crystallizing in the GdRuAl-type hexagonal crystal structure, by measurements in the range 1.8-300 K with bulk experimental techniques (ac and dc magnetization, heat capacity, and magnetoresistance). The main finding is that the Tb compound, known to order antiferromagnetically below (T =) 22 K, shows glassy characteristics at lower temperatures ([Formula: see text]15 K), thus characterizing this compound as a re-entrant spin-glass.

Pyrocurrent anomalies and intrinsic magnetodielectric behavior near room temperature in LiNiMoO, a compound with distorted honeycomb and spin-chains.

Keeping current interests to identify materials with intrinsic magnetodielectric behaviour near room temperature and with novel pyroelectric current anomalies, we report temperature and magnetic-field dependent behavior of complex dielectric permittivity and pyroelectric current for an oxide, LiNiMoO, containing magnetic ions with (distorted) honey-comb and chain arrangement and ordering magnetically below 8 K. The dielectric data reveal the existence of relaxor ferroelectricity behaviour in the range 160-240 K and there are corresponding Raman mode anomalies as well in this temperature range. Pyrocurrent behavior is also consistent with this interpretation, with the pyrocurrent peak-temperature interestingly correlating with the poling temperature.

Enhancement of magnetic ordering temperature and magnetodielectric coupling by hole doping in a multiferroic DyFeCrO.

We report the results of our investigation of magnetic, thermodynamic and dielectric properties of Ca substituted half-doped orthochromite, DyCaFeCrO. Magnetic susceptibility and heat capacity data bring out that this compound undergoes two antiferromagnetic transitions, one at ~132 and the other at ~22 K. These values are higher than those of DyFeCrO.

Effect of rare-earth (Er and Gd) substitution on the magnetic and multiferroic properties of DyFe0.5Cr0.5O3.

We report the results of our investigations on the influence of partial substitution of Er and Gd for Dy on the magnetic and magnetoelectric properties of DyFe0.5Cr0.5O3, which is known to be a multiferroic system.

A rock-salt-type Li-based oxide, Li3Ni2RuO6, exhibiting a chaotic ferrimagnetism with cluster spin-glass dynamics and thermally frozen charge carriers.

The area of research to discover new Li containing materials and to understand their physical properties has been of constant interest due to applications potential for rechargeable batteries. Here, we present the results of magnetic investigations on a Li compound, Li3Ni2RuO6, which was believed to be a ferrimagnet below 80 K. While our neutron diffraction (ND) and isothermal magnetization (M) data support ferrimagnetism, more detailed magnetic studies establish that this ferrimagnetic phase exhibits some features similar to spin-glasses.

Spin-glass behavior and pyroelectric anomalies in a new lithium-based oxide, Li3FeRuO5.

The results of dc and ac magnetization, heat capacity, (57)Fe Mössbauer spectroscopy, dielectric, pyroelectric current and isothermal magneto-capacitance measurements of a recently reported lithium-rich layered oxide, Li3FeRuO5, related to LiCoO2-type (rhombohedral, space group R3[combining macron]m), are presented. The results reveal that the compound undergoes spin-glass freezing at 15 K. There is a peak around 34 K in pyroelectric data, which cannot be attributed to ferroelectricity, but to the phenomenon of thermally stimulated depolarization current.

Magnetic behavior of GdRuAl, a layered compound with distorted kagomé net.

The magnetic behavior of the compound, GdRuAl, which was reported about two decades ago to crystallize in a hexagonal structure (space group P6/mmc), has not been investigated in the past literature despite interesting structural features (that is, magnetic layers and triangular as well as kagomé-lattice features favoring frustrated magnetism) characterizing this compound. We report here the results of studies of magnetization, heat capacity and magnetoresistance in the temperature range T  =  1.8-300 K.

Displacive-type ferroelectricity from magnetic correlations within spin-chain.

Observation of ferroelectricity among non-d(0) systems, which was believed for a long time an unrealistic concept, led to various proposals for the mechanisms to explain the same (i.e. magnetically induced ferroelectricity) during last decade.

A reentrant phenomenon in magnetic and dielectric properties of Dy2BaNiO5 and an intriguing influence of external magnetic field.

We report that the spin-chain compound Dy2BaNiO5, recently proven by us to exhibit magnetoelectric coupling below its Néel temperature (TN) of 58 K, exhibits strong frequency-dependent behavior in ac magnetic susceptibility and complex dielectric properties at low temperatures (<10 K), mimicking the 'reentrant' multiglass phenomenon. Such a behavior is not known among undoped compounds. A new finding in the field of multiferroics is that the characteristic magnetic feature at low temperatures moves towards higher temperatures in the presence of a magnetic field (H), whereas the corresponding dielectric feature shifts towards lower temperatures with H, unlike the situation near TN.

Modifications in the frustrated magnetism, oxidation state of Co and magnetoelectric coupling effects induced by a partial replacement of Ca by Gd in the spin-chain compound Ca3Co2O6.

We have systematically investigated the influence of the gradual replacement of Ca by Gd on the magnetic and complex dielectric properties of the well-known geometrically frustrated spin-chain system Ca3Co2O6 (TN = 24 K with additional magnetic transitions below 12 K), by studying the series Ca3−xGdxCo2O6 (x ≤ 0.7), down to 1.8 K.

Novel dielectric anomalies due to spin-chains above and below Néel temperature in Ca3Co2O6.

We bring out novel dielectric behavior of a spin-chain compound, Ca3Co2O6, undergoing Néel order at (TN = ) 24 K. It is found that the virgin curve in the plot of isothermal dielectric constant (ε') versus magnetic-field lies outside the 'butterfly-shaped' envelope curve well below TN (e.g.

The nature of 4f electron magnetism in the diluted ferromagnetic Kondo lattice, CeIr2B2.

We report on the physical properties of the series Ce(1-x)La(x)Ir(2)B(2) (x = 0-0.9), obtained by means of magnetization, heat capacity and electrical resistivity measurements as a function of temperature (down to 0.7 K for the latter two measurements).

Magnetic anomalies in CeIn(2).

The magnetic behavior of binary compound CeIn(2) has been reported to be unusual in the sense that this compound appears to exhibit a first-order ferromagnetic transition at a rather high temperature of (T(C)=)22 K, which is not so common for Ce systems. In order to throw more light on the magnetic behavior of this compound, we have carried out detailed magnetization, and electrical resistivity studies as a function of temperature, magnetic field and external pressure, in addition to heat-capacity measurements. The plots of H/M versus M(2) at low fields are interestingly characterized by negative slopes, not only near T(C), but also at lower temperatures, a source of which could be attributed to magnetic-field-induced transitions at much lower temperatures.

Large variations in the magnetic ordering behavior of EuCu(2)As(2) with the application of external pressure and magnetic field.

The influence of external pressure on the electrical transport and magnetic properties of EuCu(2)As(2), crystallizing in a ThCr(2)Si(2)-type structure, is reported. The system is known to be an antiferromagnet below T(N) ≈ 15 K in the absence of external magnetic fields. We find that there is a gradual reduction of T(N) with the application of a magnetic field with an extrapolated value of the critical field of around 18 kOe which can drive T(N) to zero.

A first-order magnetic phase transition near 15 K with novel magnetic-field-induced effects in Er5Si3.

We present magnetic characterization of a binary rare-earth intermetallic compound Er(5)Si(3), crystallizing in Mn(5)Si(3)-type hexagonal structure, through magnetization, heat capacity, electrical resistivity and magnetoresistance measurements. Our investigations confirm that the compound exhibits two magnetic transitions with decreasing temperature, the first one at 35 K and the second one at 15 K. The present results reveal that the second magnetic transition is a disorder-broadened first-order transition, as shown by thermal hysteresis in the measured data.

Evolution of a metastable phase with a magnetic phase coexistence phenomenon and its unusual sensitivity to magnetic field cycling in the alloys Tb(5 - x)Lu(x)Si3 (x ≤ 0.7).

Recently, we reported an anomalous enhancement of the positive magnetoresistance beyond a critical magnetic field in Tb(5)Si(3) in the magnetically ordered state, attributable to 'inverse metamagnetism'. This results in unusual magnetic hysteresis loops for the pressurized specimens, which are relevant to the topic of 'electronic phase separation'. In this paper, we report the influence of small substitutions of Lu for Tb, to show the evolution of these magnetic anomalies.

Enhanced electrical resistance at the field-induced magnetic transitions in some non-stoichiometric and stoichiometric Tb-based ternary germanides.

We present the magnetic and transport behavior of some Tb compounds, namely TbIrGe(2), TbFe(0.4)Ge(2) and TbCo(0.4)Ge(2).

Magnetic behavior of bulk and fine particles of RCr2Si2C (R = La, Ce) compounds: possible magnetic ordering from Cr.

The magnetic behavior of the quaternary compounds, RCr(2)Si(2)C (R = La, Ce), has been investigated by magnetization (M) and heat-capacity (C) measurements (1.8-300 K) in the bulk polycrystals and nano forms (<1 µm) obtained by high-energy balling. Our finding is that Cr appears to exhibit magnetic ordering of an itinerant type at low temperatures (<20 K) in the bulk form, as inferred from a combined look at all the data.

Importance of conduction electron correlation in a Kondo lattice, Ce₂CoSi₃.

Kondo systems are usually described by the interaction of the correlation induced local moments with the highly itinerant conduction electrons. Here, we study the role of electron correlations among conduction electrons in the electronic structure of a Kondo lattice compound, Ce₂CoSi₃, using high resolution photoemission spectroscopy and ab initio band structure calculations, where Co 3d electrons contribute in the conduction band. High energy resolution employed in the measurements helped to reveal the signatures of Ce 4f states derived Kondo resonance features at the Fermi level and the dominance of Co 3d contributions at higher binding energies in the conduction band.

Magnetism of fine particles of Kondo lattices, obtained by high-energy ball-milling.

Despite intense research in the field of strongly correlated electron behavior for the past few decades, there has been very little effort to understand this phenomenon in nanoparticles of the Kondo lattices. In this paper, we review the results of our investigation on the fine particles (<<1 μm) of some of the alloys obtained by high-energy ball-milling, to bring out that this synthetic method paves a way to study strong electron correlations in nanocrystals of such alloys. We primarily focus on the alloys of the series CeRu(2 - x)Rh(x)Si2, lying at different positions in Doniach's magnetic phase diagram.