Nonmagnetic Zn Research Articles

Permeability modulation of Fe-Ni/nanoparticle (Ni, Zn) soft magnetic composites

In this study, we investigated how adding nanopowders to a micropowder affects the packing fraction and permeability. The micropowder used was a Fe-Ni crystalline alloy, which was sieved to less than 38 μm to minimize the effect of particle size distribution. The nanopowders, magnetic Ni and nonmagnetic Zn, were added to the Fe-Ni at weight ratios of 95:5, 90:10, 85:15, and 80:20. The results showed that the permeability of Fe-Ni was higher when sieved to 38 μm compared to the overall particle size. When the magnetic Ni nanopowder was added to the Fe-Ni powder sieved to 38 μm, both the packing fraction and permeability increased up to a ratio of 85:15 and then decreased. On the other hand, when the nonmagnetic Zn nanopowder was added, the packing fraction increased up to a ratio of 85:15 and then decreased, while the permeability continued to decrease.

Dopant site occupancies and iron valence states in SrZnxFe18−xO27 W-type hexaferrites using site-selective X-ray/electron spectroscopy

Zn-doped W-type Sr hexaferrite (SrZnxFe18−xO27; SrZnx-WHF) is an anticipated rare-earth-free hard magnetic material with strong magnetocrystalline anisotropy and saturation magnetization. To examine the origin of its high magnetic performance, the site distribution of Zn over seven crystallographically inequivalent Fe sites and the site-dependent valence states of Fe were investigated using site-selective elemental/chemical analysis techniques. The dominant occupation of Zn2+ at the 4etet(S) and 4ftet(S) tetrahedral sites was determined quantitatively using high-angular-resolution electron-channeling X-ray spectroscopy and statistical data analysis. The combined application of high-angular-resolution electron channeling electron spectroscopy and atomic-column resolution scanning transmission electron microscopy–electron energy-loss spectroscopy helped unambiguously clarify that most of the Fe2+ ions existed at the 6goct(S-S) octahedral site. Density functional theory calculations have shown that Zn doping leads to a redistribution of the charges toward Fe ions at this site. This redistribution preserves the local charge balance and amplifies the total number of parallel spins. Hence, the enhanced magnetocrystalline anisotropy and saturation magnetization in SrZnx-WHF can be inferred to originate from the charge redistribution at the 6goct(S-S) site, which is influenced by the presence of nonmagnetic Zn.

Effects on magnetocaloric and magnetoresistive properties due to nonmagnetic Zn2+ substitution at Mn-site in charge-ordered Pr0.5Ca0.5MnO3 manganite

This study of nonmagnetic Zn-substitution effect on the charge-ordered behavior of Pr0.5Ca0.5Mn1-xZnxO3 (x = 0.0, 0.1) compounds reveal the weakening of strong charge-ordered antiferromagnetic state of the parent compound (x = 0.0). Magnetocaloric effect (MCE) has been calculated using a Python package from isothermal M-H data for these samples. A prominent ferromagnetic contribution in the antiferromagnetic matrix for Mn-site doping is observed, which removes the inverse MCE observed in the pristine sample below the charge ordering temperature TCO. Development of ferromagnetism in the doped system exhibits a metal-insulator transition at TMI = 90 K under 7 T magnetic field and large magnetoresistance (> 99 %), which is not observed in parent compound. Magnetic field-dependent hysteresis at low temperature reveals the ferromagnetic metastability and first-order nature of magnetic phase transition. Random occupation of Zn at the Mn-site of the parent compound disrupts 1:1 Mn3+/Mn4+ charge-ordered superstructure of the parent compound which weakens the charge-ordered antiferromagnetic strength promoting ferromagnetism and double-exchange interaction through an enhanced 2p-3d hybridization between Mn and O ions.

Tuning the Superspin Dynamics in Inverse Spinel Ferrite Nanoparticle Ensembles via Indirect Cation Substitution

We used magnetic and synchrotron X-ray diffraction measurements to investigate the possibility of tuning the strength of magnetic interparticle interactions in nanoparticle ensembles via chemical manipulation. Our main result comes from temperature-resolved in-phase ac-susceptibility data collected on 8 nm average-diameter Ni0.25Zn0.75Fe2O4 (Ni25) and Ni0.5Zn0.5Fe2O4 (Ni50) nanoparticles at different frequencies, χ′ vs. T|f. We found that the relative peak temperature variation per frequency decade, ϕ=∆TT·∆log(f)—a known measure of interparticle interaction strength—exhibits a four-fold increase, from ϕ = 0.04 in Ni50 to ϕ = 0.16 in Ni25. This corresponds to a fundamental change in the nanoparticles’ superspin dynamics, as proven by the fit of phenomenological models to magnetic relaxation data. Indeed, the Ni25 ensemble exhibits superparamagnetic behavior, where the temperature dependence of the superspin relaxation time, τ, is described in the Dorman–Bessais–Fiorani (DBF) model: τT=τrexp⁡EB+EadkBT, with parameters τr = 4 × 10−12 s, and (EB + Ead)/kB = 1473 K. On the other hand, the nanoparticles in the Ni50 ensemble freeze collectively upon cooling in a spin-glass fashion according to a critical dynamics law: τ(T)=τ0TTg−1zν, with τ0 = 4 × 10−8 s, Tg = 145 K, and zν = 7.2. Rietveld refinements against powder X-ray diffraction data reveal the structural details that underlie the observed magnetic behavior: an indirect cation replacement mechanism by which non-magnetic Zn ions are incorporated in the tetrahedral sites of the inverse spinel.

Zn-Ti co-substituted LiZn microwave ferrites: Sintering characteristics and gyromagnetic properties

To meet the low-loss and high-frequency application requirements of modern electronic information systems for integrated microwave devices, Zn-Ti co-substituted LiZn microwave ferrites were prepared in this work. The results demonstrated that Zn-Ti co-substitution promoted the grain growth and densification process during sintering, leading to a decrease in the pore-induced linewidth (ΔHp) of LiZn composite microwave ferrites; the introduction of non-magnetic Zn2+ and Ti4+ ions lowered the content of Fe3+ ions in the ferrites, which reduced the magnetocrystalline anisotropy constant |K1| and thus diminished the anisotropy-induced linewidth (ΔHa). Besides, the dielectric loss of the material decreased with increasing Zn-Ti substitution amounts (x) due to the reduction of Fe2+ ion content. As a result, when x = 0.35, the FMR linewidth was decreased from ∼251 Oe to ∼97 Oe, and the dielectric loss was greatly reduced from >100×10−4 to ∼3.82×10−4 in the ferrites. The material also exhibited excellent properties including high saturation magnetization (∼3913 Gauss), high Curie temperature (∼304 °C), and low coercivity (∼2.05 Oe).

The enhanced oxidation resistance of zinc-coated Nd-Fe-B spherical powders using a rotation coating technique

A rotation coating technique was used to apply Zn layer onto MQP-S Nd-Fe-B spherical powders, aiming to enhance their anti-oxidation properties while maintaining their high magnetic performance. As the coating temperature increases and duration extends, the Zn layer thickness grows, subsequently leading to a reduction in powder magnetization primarily due to the introduction of nonmagnetic Zn. A certain level of degradation of the original Nd-Fe-B powders also occurs during coating, which appears to be relatively minor, as the powders' coercivity remains almost unchanged after coating. All powders coated under different conditions effectively prevent further oxidation, maintaining almost unaltered magnetization during high-temperature tests. It demonstrates that rotation coating using lower melting point metals is a simple yet effective method to enhance the anti-oxidation capability of Nd-Fe-B powders. Moreover, this approach is easily scalable, which is important for applications in fabricating metal injection molding or bonded magnets.

Effect of divalent metal ions substitution on the magnetic properties of Ba3Co2-xMexFe24O41 (Me = Zn2+, Ni2+) hexagonal ferrites

With the high-frequency development of communication technology, traditional communication materials have been difficult to meet the application requirements. Z-type hexagonal ferrite materials are widely used as good magnetic dielectric materials in high-frequency communication applications due to their high cut-off frequency and magnetodielectric properties. However, the high-frequency magnetodielectric properties need to be further improved, so the magnetic properties of the divalent metal ion-substituted Co2Z hexagonal ferrite materials are studied, and the anisotropy is calculated according to its static magnetic properties in this paper. A series of the ferrites Ba3Co2-xMexFe24O41(Me = Zn2+, Ni2+, where x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0) were prepared by high-energy ball milling and sintering at 1260℃ for 3 h. The structural and magnetic properties of the samples were investigated using X-ray diffraction, vibrating sample magnetometer, and vector network analyzer. The studies indicated that the magnetic Ni2+ ions substitution increases the cutoff frequency, and the nonmagnetic Zn2+ ions substitution plays a positive role in increasing the magnetic permeability. Particularly, the Ba3Co1.6Ni0.4Fe24O41 and Ba3Co1.2Zn0.8Fe24O41 both have equal permeability and permittivity about 9 and 12, and their cutoff frequency exceed 2 GHz and 1 GHz, respectively. At the same time, these isomagnetic dielectric materials also have low loss, which will have great application potential in microstrip antennas.

The role of Sn and Zn substitutions on the magnetic properties of nanosized Y-type hexaferrite prepared by sol-gel auto-combustion method

The current paper has focused on the improvement of the magnetic performance of the Sn, Zn-doped Y-type hexaferrite nanoparticles via the sol–gel auto-combustion method. The partial replacement of nonmagnetic Zn2+ and Sn4+ cations for the magnetic Fe3+ cation was studied. At the low Zn-Sn concentration, the Sn4+ cations had a preference for octahedral locations (12k, 2a, 4f2) and the Zn2+ cations had a strong tendency to move to the tetrahedral spaces (4f1), respectively. Based on this data, the single-phase hexaferrites with the chemical formula of Sr2Co1.7Mg0.3Fe(12-x)Snx/2Znx/2O22 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were successfully synthesized via the sol–gel auto-combustion method. The x-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Thermal Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), Field Emission Scanning Electron Microscopy (FESEM) and Vibrating Sample Magnetometer (VSM) were carried out to investigate the obtained ferrite performance. The results revealed the formation of the single-phase platelet-like Y-type hexagonal ferrites after calcinations at 1000 °C with a thickness of 30–70 nm and a particle size of 90–210 nm. The obtained nanosized ferrites had the magnetic coercivity (Hc) and the saturation magnetization (Ms) in the range of 2100–637 Oe and 38–48 emu g−1, respectively. The addition of Sn, Zn dopants enhanced the saturation magnetization and reduced the magnetic coercivity, which can make this ferrite a candidate for some applications.

Suppression of critical temperature and superfluid phase stiffness by magnetic Ni and nonmagnetic Zn in Y3Ba5Cu8O18–δ superconductors

Suppression of critical temperature and superfluid phase stiffness by magnetic Ni and nonmagnetic Zn in Y3Ba5Cu8O18–δ superconductors

Effect of ZnO on the Structural and Magnetodielectric Properties of MgFe2O4 Nanocomposite Prepared by Sol-Gel Method

Zinc oxide doped magnesium ferrite (Mg1-xZnxFe2O4) nanocomposite was synthesized using sol-gel method and demonstrated to have a cubic spinel structure, with a range of crystallite sizes (19-40 nm) and lattice constants (8.432-8.399 Å). The material was found to have two prominent vibrational modes for tetrahedral (446 cm–1) and octahedral (584 cm–1). The dielectric constant was higher at low frequencies and decreased at higher frequencies, while the saturation magnetization decreased (16 to 6 emu/g) gradually with an increase in Zn2+, likely due to the presence of non-magnetic Zn2+. The magneto-dielectric constant was found to increase with the magnetic field for MgFe2O4 and up to a magnetic field of 2000 Oe for the zinc magnesium nanocomposites, after which it decreased for higher magnetic fields. A positive and negative change in magneto-capacitance as a function of the magnetic field was also observed. The antibacterial activity suggests that the substitution of Zn2+ into magnesium ferrite can be an effective method for improving antibacterial activity, with the potential to damage the bacterial membrane and other components through positively charged ions and ROS generated by nanoparticles. Potential uses for this synthetic material include magneto-optical recording and magnetic biosensors.

Effects of Nonmagnetic Zn2+ Ion and RE Ion Substitution on the Magnetic Properties of Functional Nanomaterials Co1-yZnyRExFe2-xO4 (RE = La, Sm, Gd) by Sol-Gel.

Magnetic Functional Nanomaterials Co1-yZnyRExFe2-xO4 (RE (rare-earth) = La,Sm,Gd) were prepared using the sol-gel combustion method. XRD characterization confirms that the ferrite samples we synthesized are single-phase cubic structures. The variation in the average crystalline size and lattice parameter is related to RE ion doping. The Mössbauer spectra of CoRExFe2-xO4 are two sets of magnetic six-wire peaks that indicate the ferrimagnetic behavior of the sample. The calcination temperature greatly influences the absorption area of Mössbauer for CoFe2O4, indicating that the calcination temperature affects the iron ion content at the octahedral B and tetrahedral A sites. Additionally, scanning electron microscopy measurements of the substituted specimens reveal that the ferrite powders are nanoparticles. With an increase in RE ions, the coercivity increases, and the saturation magnetization changes obviously. The XRD characterization of Co0.7Zn0.3LaxFe2-xO4 shows that the main crystalline phase of the sample is the cubic spinel structure phase, and there are fewer secondary crystalline phases. The lattice parameter tends to decrease with the substitution of La3+ ions. The average grain size decreased significantly with the increase in La content. From ferrimagnetic state transition to relaxation behavior, the hyperfine magnetic field decreases in La concentration by room temperature Mössbauer spectra. With the substitution of La3+ ions, both the saturation magnetization and coercivity of the samples were reduced, and the coercivity of all samples was lower.

Role of oxygen potential in dopant solubility in ferrite magnets: Enhanced Zn solubility and magnetization in La–Zn co-substituted magnetoplumbite-type strontium ferrite

To improve the performance of magnetoplumbite-type (M-type) AFe12O19 (A = Sr, Ba, Pb,…) hard ferrite magnets, such as the remanent magnetization and the coercivity, it is effective to dope transition metal elements at the Fe site. Substitution of nonmagnetic Zn, which preferentially occupies a minority-spin site in the ferrimagnets, is expected to increase magnetization. However, the solubility of Zn is limited to approximately 2–3% of Fe when synthesized in air. The solubility of divalent transition-metal substituents achieved by simultaneous substitution with trivalent cations on the A-site is often limited due to the auto reduction of Fe3+ to Fe2+. In this study, La–Zn co-substituted M-type strontium ferrites, Sr1−xLaxFe12−yZnyO19, were synthesized under different oxygen pressures of pO2 = 0.2, 1, and 10 atm, and the phase equilibrium and chemical composition were established by X-ray diffraction and wavelength dispersive X-ray spectroscopy. At pO2 = 10 atm, Sr-free La–Zn co-substituted ferrite, LaFe11.25Zn0.75O19, and single phases with actual compositions (x, y) = (0.42, 0.33) and (0.50, 0.45) were obtained for the first time. The single-phase samples exhibited a 5–9% higher saturation magnetization compared to non-doped SrFe12O19 at room temperature. Together with the coercivity enhancement by Co2+ substitution, oxygen potential control is a promising strategy to tune both coercivity and magnetization in future ferrite magnets.

Spin chiral interactions modulated Seebeck coefficient and improved optical properties by Zn doping in CuCrO2 crystallites

Future electronics hold a special promise for flexible, optically translucent thermoelectric devices. Here, we demonstrate the better thermoelectric performance of p-type transparent CuCrO2 crystallites by the insertion of non-magnetic Zn2+ in magnetic Cr3+ site at room and high temperatures. Doping induced increase in charge carrier density generally leads to elevated carrier scattering, which in turn diminishes the voltage generated per unit tem-perature difference and causes a decrease in the Seebeck coefficient. Balancing the Seebeck coefficient and conductivity is a crucial challenge in the design of thermoelectric materials. By introducing non-magnetic doping, the anti-ferromagnetic order of Cr3+ ions is destabilized, resulting in a modification of the spin configuration. This alteration gives rise to spin chiral interactions, which, in turn, contribute to the generation of an exceptionally large Seebeck coefficient of 582 μV/K at 100 °C. The insertion also generates anisotropic microstrains in the structure and the structural changes were investigated by XRD analysis, FTIR, and Raman spectroscopy. Carrier concentration and carrier mobility were measured by Hall measurements techniques and has shown increasing and decreasing trend respectively with the increase of the doping percentage of Zn2+. Optical studies were done by UV–Vis analysis and found the maximum band gap of 3.04 eV for 0.5 wt% doped CuCrO2 and the absorption spectra revealed the defect induced in the structure comprehending the Raman analysis. The enhancement of carrier concentration and mobility led to increased conductivity of 2096 S/m and power factor of 411 μW/mK2 for the sample 0.3 wt% at 700 °C. The Seebeck coefficient of the sample dropped as the temperature rose, but it was maintained in the range of 440–580 μV/K, which is found as the primary characteristic of Zn doping. Thermal conductivity is found as decreased with doping and the highest ZT obtained is 0.199 for 0.3 wt% doped sample at 700 °C. The higher thermoelectric performance and optical transmission at visible wavelength can be put together in optoelectronic devices.

The role of Zn and Ru substitution on the structural, magnetic and dielectric properties of ferrite cuprospinels

A comprehensive study on the structural, magnetic and dielectric behavior of ferrite cuprospinels with site specific substitution of non-magnetic Zn and weakly magnetic Ru ions has been presented. Such substitution leads to two classes of stable crystal symmetries, (i) tetragonal (I41/amd): CuFe1.95Ru0.05O4 and Cu0.95Zn0.05Fe1.95Ru0.05O4 and (ii) cubic (Fd-3m):Cu0.60Zn0.40Fe1.95Ru0.05O4 and Cu0.05Zn0.95Fe1.95Ru0.05O4 bulk polycrystals. The former set of compounds undergo significant Jahn-Teller (JT) distortion due to high Cu content and such distortion gets lifted with the substitution of non-magnetic Zn ions. Ferrimagnetic (FiM) behavior is predominant in all these compounds except the highest Zn (95 at.%) content cubic system with diluted substitution of Ru (2.5 at.%) which exhibits antiferromagnetic ordering below the Néel temperature (T N ∼ 10.9 K). We employed Néel’s expression for FiM systems applicable for the two sublattice model to extract the dominant exchange interactions (J AA , J AB and J BB ) between the A-site and B-site cations. Subsequently the high temperature (300 K T 900 K) inverse paramagnetic susceptibility data has been fitted to the above expression which yields dominant ∼ 391 K with very high asymptotic Curie temperature for the tetragonally distorted dilute Zn substituted cuprospinel, while the Zn-rich cubic system exhibits ∼ 300 K. On the other hand, the tetragonally distorted spinel devoid of Zn exhibits dominant ∼ 229 K with negligible and moderate (65 K) signifying that the JT active ions cause the onset of magnetic frustration and enhanced ordering temperatures. All the investigated systems exhibit significant magneto-crystalline anisotropy with a maximum anisotropy field H K ∼ 6 kOe and maximum anisotropy constant (K 1 ∼ 10.88×105 erg cm−3). The broadband dielectric spectroscopy studies reveal significant enhancement of mid-frequency dielectric constant ε R (f, T) with plateau-like feature over a wide temperature and frequency window, together with low-loss as a result of the incorporation of Ru ions into the tetragonally distorted spinel lattice. The ac resistivity ρ(f, T) studies reveal that the mode of conduction follows Mott’s variable-range hopping (VRH) model with a linear logarithmic variation of ρ ac versus T −0.25. The temperature dependence of the VRH activation energy of charge carriers follows a linear behavior which indicates the presence of localized polaron in all the investigated systems.

Signatures of a gapless quantum spin liquid in the Kitaev material Na3Co2−xZnxSbO6

The honeycomb-lattice cobaltate Na$_3$Co$_2$SbO$_6$ has recently been proposed to be a proximate Kitaev quantum spin liquid~(QSL) candidate. However, non-Kitaev terms in the Hamiltonian lead to a zigzag-type antiferromagnetic~(AFM) order at low temperatures. Here, we partially substitute magnetic Co$^{2+}$ with nonmagnetic Zn$^{2+}$ and investigate the chemical doping effect in tuning the magnetic ground states of Na$_3$Co$_{2-x}$Zn$_x$SbO$_6$. X-ray diffraction characterizations reveal no structural transition but quite tiny changes on the lattice parameters over our substitution range $0\leq x\leq0.4$. Magnetic susceptibility and specific heat results both show that AFM transition temperature is continuously suppressed with increasing Zn content $x$ and neither long-range magnetic order nor spin freezing is observed when $x\geq0.2$. More importantly, a linear term of the specific heat representing fermionic excitations is captured below 5~K in the magnetically disordered regime, as opposed to the $C_{\rm m}\propto T^3$ behavior expected for bosonic excitations in the AFM state. Based on the data above, we establish a magnetic phase diagram of Na$_3$Co$_{2-x}$Zn$_x$SbO$_6$. Our results indicate the presence of gapless fractional excitations in the samples with no magnetic order, evidencing a potential QSL state induced by doping in a Kitaev system.

Observation of coherently coupled cation spin dynamics in an insulating ferrimagnetic oxide

Many technologically useful magnetic oxides are ferrimagnetic insulators, which consist of chemically distinct cations. Here, we examine the spin dynamics of different magnetic cations in ferrimagnetic NiZnAl-ferrite (Ni0.65Zn0.35Al0.8Fe1.2O4) under continuous microwave excitation. Specifically, we employ time-resolved x-ray ferromagnetic resonance to separately probe Fe2+/3+ and Ni2+ cations on different sublattice sites. Our results show that the precessing cation moments retain a rigid, collinear configuration to within ≈2°. Moreover, the effective spin relaxation is identical to within <10% for all magnetic cations in the ferrite. Thus, we validate the oft-assumed “ferromagnetic-like” dynamics in the resonantly driven ferrimagnetic oxide: the magnetic moments from different cations precess as a coherent, collective magnetization, despite the high contents of nonmagnetic Zn2+ and Al3+ diluting the exchange interactions.

Partitioning the Two-Leg Spin Ladder in Ba2Cu1-x Zn x TeO6: From Magnetic Order through Spin-Freezing to Paramagnetism.

Ba2CuTeO6 has attracted significant attention as it contains a two-leg spin ladder of Cu2+ cations that lies in close proximity to a quantum critical point. Recently, Ba2CuTeO6 has been shown to accommodate chemical substitutions, which can significantly tune its magnetic behavior. Here, we investigate the effects of substitution for non-magnetic Zn2+ impurities at the Cu2+ site, partitioning the spin ladders. Results from bulk thermodynamic and local muon magnetic characterization on the Ba2Cu1-x Zn x TeO6 solid solution (0 ≤ x ≤ 0.6) indicate that Zn2+ partitions the Cu2+ spin ladders into clusters and can be considered using the percolation theory. As the average cluster size decreases with increasing Zn2+ substitution, there is an evolving transition from long-range order to spin-freezing as the critical cluster size is reached between x = 0.1 to x = 0.2, beyond which the behavior became paramagnetic. This demonstrates well-controlled tuning of the magnetic disorder, which is highly topical across a range of low-dimensional Cu2+-based materials. However, in many of these cases, the chemical disorder is also relatively strong in contrast to Ba2CuTeO6 and its derivatives. Therefore, Ba2Cu1-x Zn x TeO6 provides an ideal model system for isolating the effect of defects and segmentation in low-dimensional quantum magnets.

Double dome structure of the Bose–Einstein condensation in diluted S = 3/2 quantum magnets

Bose–Einstein condensation (BEC) in quantum magnets, where bosonic spin excitations condense into ordered ground states, is a realization of BEC in a thermodynamic limit. Although previous magnetic BEC studies have focused on magnets with small spins of S ≤ 1, larger spin systems potentially possess richer physics because of the multiple excitations on a single site level. Here, we show the evolution of the magnetic phase diagram of S = 3/2 quantum magnet Ba2CoGe2O7 when the averaged interaction J is controlled by a dilution of magnetic sites. By partial substitution of Co with nonmagnetic Zn, the magnetic order dome transforms into a double dome structure, which can be explained by three kinds of magnetic BECs with distinct excitations. Furthermore, we show the importance of the randomness effects induced by the quenched disorder: we discuss the relevance of geometrical percolation and Bose/Mott glass physics near the BEC quantum critical point.

Effect of Zn2+-Sn4+ co-substitution on structural and magnetic properties of SrFe12-2xZnxSnxO19 (x = 0–2) M-type strontium ferrite

We studied the structure and magnetic properties of Zn2+-Sn4+ co-substituted M-type strontium ferrite by X-ray diffraction (XRD), Fourier transformer infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and superconducting quantum interference device magnetometer (SQUID-VSM). The lattice constants a and c increase monotonically with increasing substitution x, which is primarily attributed to the fact that the ionic radii of Zn2+ and Sn4+ are larger than those of Fe3+. The room temperature magnetic measurement results indicate that the saturation magnetization (Ms) can reach the maximum value Ms = 77 emu/g when x = 0.25, originating from the occupation of Zn2+ and Sn4+ in the spin-down 4f1 and 4f2 sites, respectively. Next, when x ≥ 0.5, the nonmagnetic Zn2+ and Sn4+ weaken the superexchange interaction, resulting in a monotonic decrease in saturation magnetization and coercivity. The sample with x = 0.25 has the optimum magnetic properties of Ms = 77 emu/g, Mr = 35 emu/g and Hc = 2203 Oe, and it is a promising candidate for high-density magnetic recording materials.

Structural phase transformation of quantum spin liquid herbertsmithite via pressure induced enhancement of the cooperative Jahn-Teller effect and antisite disorder.

Herbertsmithite, Cu3Zn(OH)6Cl2, serves as one of the most promising candidates for quantum spin liquids with a perfect quantum kagome Heisenberg antiferromagnetic system. It can comprise an ideal model system for studying the compression response of the unique structure as well as exotic properties of kagome quantum spin liquid materials, which is of fundamental importance from both scientific and technological viewpoints. In this work, the structural evolution of herbertsmithite was investigated via in situ X-ray diffraction and Raman scattering techniques up to 30 GPa. The trigonal herbertsmithite structure transformed into a monoclinic clinoatacamite-like structure at 12.6 GPa. High pressure seems to act in a reverse way as Zn-doping for herbertsmithite, with the distortion degree of the system changing continuously. The occurrence of the displacive and reversible phase transition between the polymorphs is a consequence of the interplay between the external pressure and cooperative Jahn-Teller (JT) effect, aided by the presence of antisite mutual substitution of magnetic Cu2+ ions and nonmagnetic Zn2+ ions between the kagome layer and interlayer sites.