Magnetic nanoparticlesNanoparticle and thin films have attracted considerable interest over recent decades due to their versatile applications in high-densityDensity magnetic recording, data storage, spintronics, solar cells, and sensors. Among these, cobalt ferriteCobalt ferrite (CoFeO) thin films (CoFe2O4) has emerged as a prominent material, valued for its excellent electromagnetic performance, chemical stability, mechanical hardness, and high cubicCubic magnetocrystalline anisotropyAnisotropy. Here, we investigate the structural, magnetic, and vibrational propertiesProperties of cobalt ferrite (CoFe2O4) thin filmsCobalt ferrite (CoFeO) thin films coated with gold, using Raman spectroscopyRaman spectroscopy and computational methods. The gold coatingGold coating enhances surface conductivityConductivity and stability while influencing the material's vibrational modes and magnetic anisotropyMagnetic anisotropy. Raman spectra revealed the suppression of key Raman-active modes, including 693 cm−1 (A₁g) and 465 cm−1 (F2g), reflecting restricted Fe–O vibrations at tetrahedral and octahedral sites. First-principles calculations based on Density Functional Theory (DFTDensity Functional Theory (DFT)) corroborate these findings, showing metallic bonding at the Au/CoFe2O4 interfaceInterface and enhanced magnetic moments of surface atoms. The present experimental and computational investigations highlight the tunable propertiesProperties of gold-coated CoFe2O4 films for advanced technological applications.

This study examines the effects of rare-earth (Gd3+, Tm3+) and nonmagnetic Al3+ co-doping on the structural, magnetic, and magnetocaloric properties of HoCrO3-based perovskites. Compounds Ho0.67Gd0.33CrO3, Ho0.67Gd0.33Cr0.5Al0.5O3, Ho0.67Tm0.33CrO3, and Ho0.67Tm0.33Cr0.5Al0.5O3 were synthesized by a sol-gel auto-combustion method and confirmed by XRD to crystallize in an orthorhombic Pbnm structure. Gd3+ substitution expanded the lattice, while Tm3+ and Al3+ reduced it. DFT study identified the G-type antiferromagnetic configuration as the most stable for all doped systems, with Al3+ substitution significantly reducing the AFM-FM energy gap. Magnetization data showed decreasing transition temperatures from 150.8 K (Ho0.67Gd0.33CrO3) to 120.0 K (Ho0.67Gd0.33Cr0.5Al0.5O3) and from 133.8 K (Ho0.67Tm0.33CrO3) to 113.2 K (Ho0.67Tm0.33Cr0.5O3). The maximum magnetic entropy change (-Delta Sm) reached 11.41 J/kg center dot K at 5 T for Ho0.67Gd0.33Cr0.5Al0.5O3, exceeding that of HoCrO3 (6.47 J/kg center dot K). These enhancements highlight Gd/Tm-and Al-co-doped HoCrO3 as promising candidates for low-temperature magnetic refrigeration.

Magnetism of single crystal ErMn6Sn6 is reported by means of magnetization M(T,H) measurements along and perpendicular to ab-plane. The compound orders antiferromagnetically below 347 K followed by ferrimagnetic ordering below 74 K along with a spin reorientation transition at 4 K. Distinctly different magnetoresponse of the compound along and perpendicular to ab-plane confirm the anisotropic magnetic nature. However, the temperature region bounded by two magnetic transitions with a width of 273 K is found to exhibit complex magnetic behaviour in the ab-plane as compared to that of in the c-direction. The temperature-magnetic field (T-H ) phase diagrams for H & Vert; ab and H & Vert; c reveal field-driven modulations to the magnetic ground state of ErMn6Sn6. In comparison to c-direction, the appearance of double magnetic transitions above and below magnetic phase separation transition T mps , indicate prevailing spiral spin structures within the magnetic layers. The present study directs a pathway to tune the properties of kagome systems as governed by inter-and-intra magnetic layer interactions.

The impact of Al3+, a non-magnetic element, replacing Cr3+ in the HoCrO3 perovskite on its crystal structure, magnetic characteristics, and magnetocaloric behavior has been reported. X-ray diffraction (XRD) analysis revealed octahedral distortions and changes in lattice parameters upon incorporating Al3+ ions. Magnetic studies showed that undoped and doped samples transition from a paramagnetic state to a canted antiferromagnetic state below the critical N & eacute;el temperature (T-N), associated with Cr3+-O2--Cr3+ exchange interactions. Al3+ doping in HoCrO3 lowered the T-N value because the substitution reduced the number of magnetic Cr3+ ions, diluting the magnetic sub-lattice and weakening overall magnetic interactions. Density functional theory (DFT) studies confirmed that Al3+ doping altered the magnetic configurations from AFM-G to AFM-C. The energy difference |EAFM-G - EAFM-C| for HoCrO3 was significantly higher (52 meV) than that observed for HoCr0.5Al0.5O3 (13.8 meV), indicating greater stability in the doped compound. From an application standpoint, Al3+ doping reduced coercivity and enhanced the compound's magnetocaloric effect. Specifically, the Al3+-doped HoCr0.5Al0.5O3 exhibited a change in magnetic entropy, -Delta S-m similar to 8.83 Jkg(-1)K(-1) at a 5T applied field, 36 % higher than HoCrO3 compound (-Delta S-m similar to 6.47 Jkg(-1)K(-1) at 5T) under the same conditions. This enhancement of -Delta S-m positions the Al3+-doped HoCr0.5Al0.5O3 as a promising material for magnetic refrigeration applications.

We report the structural, magnetic, and magnetocaloric properties of substitutional defect-engineered Gd3-xM'xFe5O12 garnet compound (M' = Pr3+ (x = 0.8) and Ca2+ (x = 0.5)). X-ray powder diffraction shows all samples have cubic crystal structure with space group Ia 3 d. Mossbauer spectroscopy revealed the presence of an increased paramagnetic phase in the Ca2+-doped Gd2.5Ca0.5Fe5O12 garnet, compared to a pristine and Pr3+- doped Gd2.2Pr0.8Fe5O12. A paramagnetic phase in the Ca2+-doped Gd2.5Ca0.5Fe5O12 garnet is attributed to Ca2+ doping, which changes Fe3+ to Fe4+ to maintain electroneutrality in the compound. According to a DFT study, doping with either Ca2+ or Pr3+ ions decreases the compound's overall magnetic moment compared to the pristine Gd3Fe5O12 compound and more so for the Pr3+-doped Gd3Fe5O12 due to the antiferromagnetic coupling of Pr3+ with Gd3+.The maximum magnetic entropy change, Delta Smax, estimated from isothermal magnetization data, was observed to be 3.80 Jkg-1K-1 (Tmax = 37.5K), 2.33 Jkg-1K-1 (Tmax = 52.5K), and 3.11 Jkg-1K-1 (Tmax = 42.5K) for Gd3Fe5O12, Gd2.2Pr0.8Fe5O12, and Gd2.5Ca0.5Fe5O12, respectively under 5T field and their respective relative cooling power, RCP, at the same magnetic field, are 380 J kg-1, 263 J kg-1, and 349 J kg-1. These results show that doping with a magnetic Pr3+ and non-magnetic Ca2+ significantly affects the magnetic entropy changes and cooling capacity in Gd3Fe5O12, demonstrating that substitutional defect engineering can influence its magnetocaloric properties over a wider temperature range.

The phase transitions and associated magnetic properties of Ni2Mn0.55Cu0.35Fe0.10Ga have been studied by dc magnetization and electrical resistivity measurements. A tetragonal crystal structure was identified at room temperature by powder x-ray diffraction measurements. The temperature dependence of magnetization data obtained while heating revealed two distinct transitions at 338 K and 368 K. On cooling the transitions were observed at 334 K and 355 K. The lower temperature transition showed a thermal hysteresis of ≈4 K, while the higher temperature transition exhibited a thermal hysteresis of ≈13 K. The temperature dependence of the electrical resistivity and isothermal entropy changes obtained data indicated that the transition at 338 K is a second order transition while the one at 368 K is a first order phase transition. For a field change of 5 T, a maximum entropy change of −3.5 J kg−1 K−1 has been observed. The experimental data showed that for both heating and cooling the martensitic phase transition occurred in a paramagnetic state in Ni2Mn0.55Cu0.35Fe0.10Ga.

This study investigates the microstructural and magnetocaloric characteristics of three orthochromite compounds: HoCrO3, Ho0.67Er0.33CrO3, and Ho0.67Er0.33Cr0.5Al0.5O3, synthesized via a sol-gel autocombustion method. X-ray diffraction confirmed a pure orthorhombic Pbnm structure in all samples. Replacing Ho3+ with Er3+ leads to a slight decrease in lattice constants due to their similar ionic radii. Substituting Cr3+ with the smaller Al3+ ion further reduces lattice parameters and unit cell volume. Density functional theory (DFT) calculations indicated that the G-type Antiferromagnetic (AFM-G) configuration is energetically stable for Ho0.75Er0.25CrO3 and HoCrO3, whereas the A-type Antiferromagnetic (AFM-A) configuration is the lowest energy state for Ho0.75Er0.25Cr0.5Al0.5O3. The energy difference between the most stable configuration and ferromagnetic configurations for Ho0.75Er0.25Cr0.5Al0.5O3, Ho0.75Er0.25CrO3, and HoCrO3 is 76.26, 251.07, and 235.42 meV/cell, respectively. It should be noted that adding Al3+ to the Cr3+ site significantly reduces the total energy gap (EAFM-EFM) in the HoCrO3 compound. This substitution also modified the Cr3+-O2--Cr3+ bond angles and lengths, thereby affecting the magnetic and magnetocaloric characteristics of the materials. Temperature-dependent magnetization measurements indicated a reduction in the magnetic transition temperature because of doping, with temperatures decreasing from 141 K for HoCrO3 to 136 K for Ho0.67Er0.33CrO3 and 120 K for Ho0.67Er0.33Cr0.5Al0.5O3. The maximum magnetic entropy change,-Delta Sm, determined from magnetic isotherms, increased with the substitution of Er3+ and Al3+. The-Delta Sm observed for HoCrO3, Ho0.67Er0.33CrO3, and Ho0.67Er0.33Cr0.5Al0.5O3 was 6.46 Jkg-1K-1, 8.04 Jkg-1K-1, and 9.69 Jkg-1K-1, respectively at a 5T applied field, representing a 30 % enhancement in-Delta Sm for Ho0.67Er0.33Cr0.5Al0.5O3 compared to the pure HoCrO3 compound.

Materials with magnetoelectric coupling (MEC) between ferroic orders at room temperature are an emerging field in modern technology and physics.

The LnSbTe (Ln = Lanthanides) family, like isostructural ZrSiS type compounds, has emerged as a fertile playground for exploring the interaction of electronic correlations and magnetic ordering with the nodal line band topology. Here, we report a detailed electronic band structure investigation of TbSbTe, corroborated by electrical transport, thermodynamic, and magnetic studies. Temperature-dependent magnetic susceptibility and thermodynamic transport studies indicate the onset of antiferromagnetic ordering below TN = 5.1 K. The electronic band structure study, carried out with high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements aided with density functional theory based first-principles calculations reveals presence of nodal lines in the GammaX high symmetry direction, forming a diamond-shaped nodal plane around Gamma high symmetry point. A strongly photon energy dependent nodal feature located at the X point of the surface Brillouin zone, indicating an extended nodal line along X R direction, is also observed. This study elucidates the intricate interplay among symmetry-protected band characteristics, the influence of spin orbit coupling, magnetism, and topological properties.

We performed an experimental study on the structural and magnetocaloric properties of PLA-based composite filaments of Mn0.5Fe0.5Ni0.95Cr0.05Si0.95Al0.05. X-ray diffraction patterns confirmed that the as-cast powder and the extruded filament composites exhibited the mixed hexagonal and orthorhombic crystal structures at room temperature. The dc magnetization data showed that all samples exhibited the first-order magnetic phase transition near room temperature. The entropy changes evaluated from the isothermal magnetization data peaked at 301 K for the powder sample and 322 K for the filament with 57 wt. % powder during warming. For a field change of 5 T, peak entropy changes of −5.5 J kg−1 K−1 and −1.2 J kg−1 K−1 were observed for powder and filament, respectively. The results suggested that PLA-composite additive manufacturing may be a promising technique for producing magnetocaloric coolants from brittle materials.

We report the magnetic properties of Fe-substituted Mn0.75Fe0.25NiGe by detailed magnetization measurements. Weak first-order phase transition along with kinetic-arrest-like behavior is confirmed based on the bifurcation between zero-field cooling and field-cooled warming magnetization curves, thermal hysteresis between field-cooled cooling and field-cooled warming curves, and an unusual nature of virgin M-H curve lying outside the hysteresis loop. At 2 K, it exhibits spontaneous exchange bias (SEB) of HEB similar to 132 Oe, which is larger than the conventional exchange bias in a cooling field of 80 kOe. The constructed temperature-field T-H phase diagram illustrates the diminishing magnetic phase coexistence (first-order) region and increase of ferromagnetic phase with the increase of magnetic field strength by avoiding tricriticality. SEB in the present alloy is reported to be due to the formation of local-domain interfaces of long-range ferromagnetic and spin-glass phases. In addition, the relatively smaller HSEB value is because of weak coupling between the magnetic phases at the interface. The present study stimulates interest in revisiting materials exhibiting coexisting magnetic phases in the quest for the exchange bias effect.

This manuscript reports on the structural and magnetic properties of NdCuGa3 using powder and single crystal X-ray diffraction (XRD), zero-field single crystal neutron diffraction, magnetization, and specific heat measurements. Our XRD on a single crystal specimen of NdCuGa3 confirmed that it crystallizes in the tetragonal BaNiSi3-type structure. A magnetic phase transition at TN= 3.3 K is assessed using specific heat and ac magnetic susceptibility measurements. No additional anomaly below TN down to 50 mK was detected by performing specific heat measurements. Neutron single crystal diffraction data collected at T= 300 mK confirm the antiferromagnetic phase below TN= 3.3 K with the propagation vector τ→= (0.2, 0, 0). Possible magnetic structure solutions of NdCuGa3 are discussed.

Terahertz scattering-type scanning near-field optical microscopy (THz-sSNOM) provides a noninvasive way to probe the low frequency conductivity of materials and to characterize material compositions at the nanoscale. However, the potential capability of atomic compositional analysis with THz nanoscopy remains largely unexplored. Here, we perform THz near-field imaging and spectroscopy on a model rare-earth alloy of lanthanum silicide (La–Si) which is known to exhibit diverse compositional and structural phases. We identify subwavelength spatial variations in conductivity that is manifested as alloy microstructures down to much less than 1 μ m in size and is remarkably distinct from the surface topography of the material. Signal contrasts from the near-field scattering responses enable mapping the local silicon/lanthanum content differences. These observations demonstrate that THz-sSNOM offers a new avenue to investigate the compositional heterogeneity of material phases and their related nanoscale electrical as well as optical properties.

Abstract Kagome materials are of topical interest for their diverse quantum properties linked with correlated magnetism and topology. Here, we report anomalous hydrostatic pressure (p) effect on ErMn6Sn6 through isobaric and isothermal-isobaric magnetization measurements. Magnetic field (H) suppresses antiferromagnetic T N while simultaneously enhancing the ferrimagnetic T C by exhibiting dual metamagnetic transitions, arising from the triple-spiral-nature of Er and Mn spins. Counter-intuitively, pressure enhances both T C and T N with a growth rate of 74.4 K GPa−1 and 14.4 K GPa−1 respectively. Pressure unifies the dual metamagnetic transitions as illustrated through p-H phase diagrams at 140 and 200 K. Temperature-field-pressure (T-H, T-p) phase diagrams illustrate distinct field- and pressure-induced critical points at (T cr = 246 K, H cr = 23.3 kOe) and (T cr = 435.8 K, p cr = 4.74 GPa) respectively. An unusual increase of magnetic entropy by pressure around T cr and a putative pressure-induced tricritical point pave a unique way of tuning the magnetic properties of kagome magnets through simultaneous application of H and p.

A solid solution of (1-x)BaTiO3-(x)LaFeO3 (x = 0, 0.007, 0.015, 0.031, 0.062) has been investigated for room temperature multiferroicity and magnetodielectric effect. The incorporation of La and Fe ions in ferroelectric BaTiO3 leads to increased lattice disorder and generation of oxygen vacancies that induces magnetism. A detailed correlated study using XRD, oS and Raman spectroscopy is being reported. A typical ferromagnetic and ferroelectric nature of each sample are confirmed by M-H and P-E hysteresis loops, respectively at room temperature. Temperature dependent dielectric studies reveal the decrease of transition temperature from 137 0C for undoped to room temperature for increasing substitution. The changes in the dielectric property with applied magnetic field shows the indications of magnetodielectric effect. For x = 0.015, existence of both proper ferroelectric without lossy properties and ferromagnetic properties in a single tetragonal phase makes it a perfect room temperature multiferroic material. For this sample, the magnetodielectric coupling is the strongest with Magnetocapacitance of -2.7% and Magneto loss of -0.8% at 10 kHz and 1 T. The multiferroicity and the magnetodielectric effect exhibited by this material has been correlated to the structural properties, electric and magnetic properties, changes in valence states, and oxygen vacancy (Ov).

Aluminum-doped ErCr1-xAlxO3 orthochromites prepared via autocombustion technique were investigated for their magnetic and magnetocaloric properties. X-ray diffraction confirmed that samples were orthorhombic phases with the Pbnm space group without a trace of any impurity. As analyzed via Rietveld refinement of XRD data, structural parameters such as lattice parameters, volume, bond angle, and bond lengths were affected by doping nonmagnetic Al3+ in the compound. ErCrO3 possesses the long-range antiferromagnetic ordering with a weak display ferromagnetism at TN =133 K. Low-temperature high-field magnetic study shows a decrease in Neel temperature (TN ∼ 114 K for x = 0.5), suggesting magnetic ordering suppression due to Al3+ doping. The asymptotic paramagnetic Curie temperature Tcw = −25 K suggests the predominance of antiferromagnetic interactions in ErCrO3 orthochromites, which was observed to increase with Al3+ doping. Isothermal magnetization data show changes in magnetic entropy (−ΔSMmax) and relative cooling power (RCP). The magnetic entropy change, −ΔSMmax, for ErCrO3 estimated from magnetization measurements show 11.60 J kg−1 K−1 at 11 K and a relative cooling power (RCP) of 209.4 J kg−1 at 5 T applied field. While ErCr0.75Al0.25O3 show a maximum magnetic entropy of 11.52 J kg−1 K−1 at 11 K with a 5 T applied field and RCP of 186.66 J kg−1, whereas ErCr0.5Al0.5O3 displayed −ΔSMmax of 11.63 J kg−1 K−1 at 5 K with a 5 T applied field and RCP value of 160.78 J kg−1. The results show that nonmagnetic doping, such as Al3+, could maintain the compound’s magnetocaloric property to an extent.

We report on the magnetic behaviour of Nd5Ge3 by investigating through magnetization, neutron diffraction and muon spin relaxation measurements. Temperature dependent-magnetization, muon depolarization rate (λ), initial asymmetry (A0) and the stretched exponent (β) show a clear anomaly at the Néel temperature TN ∼ 54 K. However, the short-range correlated ferromagnetic interactions below TN are inferred from the diffuse scattering mechanism as revealed by zero-field neutron diffraction data. Narrow first order phase transition is due to the competing interaction of a high temperature weak-antiferromagnetic and low temperature glassy states. Magnetic field-induced reentrant spin glass state from a magnetic glass state is observed, before it transforms to a ferromagnetic state.