Temperature Dependence Of Magnetic Susceptibility Research Articles

A mono-nuclear Cu(II) complex of an unsymmetrical Schiff base ligand and its use to synthesise trinuclear CuII2MnII complexes showing anion dependent SMM behaviour

The effort for synthesis complexes of unsymmetrical Schiff base ligands derived from 2,2-dimethyl-1,3-propanediamine, o-hydroxyacetophenone and salicylaldehyde by modified Edler's method resulted in the isolation of mononuclear [CuL]·CH3OH (1), where H2L = N-(α-methylsalicylidene)-N′-(salicylidene)-2,2-dimethyl-1,3-propanediamine. Complex 1 on reaction with Mn(II) ion in presence of ClO4−, N(CN)2−, or N3− yielded three tri-nuclear complexes [(CuL)2Mn(CH3OH)2](ClO4)2·3H2O (2) [(CuL)2Mn(N(CN)2)2] (3) and [(CuL)2Mn(N3)2]∙2H2O (4), respectively. X-ray crystallography revealed square planar geometry of Cu(II) and distorted octahedral geometry of Mn(II) in the complexes. Temperature dependent molar magnetic susceptibility measurements illustrated overall anti-ferromagnetic coupling between the Cu(II) and Mn(II) centres in complexes 2–4 with exchange coupling parameters, J = −16.82 cm−1 and g = 2.06 for 2, J = −19.40 cm−1 and g = 2.10 for 3 and J = −18.98 cm−1 and g = 2.11 for 4. Among these hetero-metallic complexes only the azide derivative (4) presented prominent ac signals under an applied dc bias field. Cyclic voltammetry measurements showed reversible Cu(II)/Cu(I) couple for complex 1 whereas complexes 2–4 showed irreversible reduction of Cu(II).

Anisotropic magnetic and transport properties of orthorhombic o-Pr2Co3Ge5

The crystal structure, electron energy-loss spectroscopy (EELS), heat capacity, and anisotropic magnetic and resistivity measurements are reported for Sn flux grown single crystals of orthorhombic Pr2Co3Ge5 (U2Co3Si5-type, Ibam). Our findings show that o-Pr2Co3Ge5 hosts nearly trivalent Pr ions, as evidenced by EELS and fits to temperature dependent magnetic susceptibility measurements. Complex magnetic ordering with a partially spin-polarized state emerges near T sp = 32 K, with a spin reconfiguration transition near T M = 15 K. Heat capacity measurements show that the phase transitions appear as broad peaks in the vicinity of T sp and T M. The magnetic entropy further reveals that crystal electric field splitting lifts the Hund’s rule degeneracy at low temperatures. Taken together, these measurements show that Pr2Co3Ge5 is an environment for complex f state magnetism with potential strongly correlated electron states.

Magnesium-rich intermetallic compounds RE 3Ag4Mg12 (RE = Y, La–Nd, Sm–Dy, Yb) and AE 3Ag4Mg12 (AE = Ca, Sr)

Abstract The magnesium-rich intermetallic compounds RE 3Ag4Mg12 (RE = Y, La–Nd, Sm–Dy, Yb) and AE 3Ag4Mg12 (AE = Ca, Sr) were synthesized from the elements in sealed tantalum ampoules through heat treatment in an induction furnace. X-ray powder diffraction studies confirm the hexagonal Gd3Ru4Al12 type structure, space group P63/mmc. Three structures were refined from single crystal X-ray diffractometer data: a = 973.47(5), c = 1037.19(5) pm, wR2 = 0.0296, 660 F 2 values, 30 variables for Gd3Ag3.82(1)Mg12.18(1), a = 985.27(9), c = 1047.34(9) pm, wR2 = 0.0367, 716 F 2 values, 29 variables for Yb3Ag3.73(1)Mg12.27(1) and a = 992.41(8), c = 1050.41(8) pm, wR2 = 0.0373, 347 F 2 values, 28 variables for Ca3Ag3.63(1)Mg12.37(1). Refinements of the occupancy parameters revealed substantial Ag/Mg mixing within the silver-magnesium substructure, a consequence of the Ag@Mg8 coordination. The alkaline earth and rare earth atoms build Kagome networks. Temperature dependent magnetic susceptibility measurements indicate diamagnetism/Pauli paramagnetism for the compounds with Ca, Sr, Y and YbII, while the others with the trivalent rare earth elements are Curie-Weiss paramagnets. Most compounds order antiferromagnetically at T N = 4.4(1) K (RE = Pr), 34.6(1) K (RE = Gd) and 23.5(1) K (RE = Tb) while Eu3Ag4Mg12 is a ferromagnet (T C = 19.1(1) K). 151Eu Mössbauer spectra confirm divalent europium (δ = −9.88(1) mm s−1). Full magnetic hyperfine field splitting (18.4(1) T) is observed at 6 K. Yb3Ag4Mg12 shows a single resonance in its 171Yb solid state NMR spectrum at 6991 ppm at 300 K indicating a strong, positive Knight shift.

Observation of thermodynamics originating from a mixed-spin ferromagnetic chain

We present a model compound that forms a mixed-spin ferromagnetic chain. Our material design, based on the organic radicals, affords a verdazyl-based complex $(p\text{\ensuremath{-}}\mathrm{Py}\text{\ensuremath{-}}{\mathrm{V})}_{2}[\mathrm{Mn}{(\mathrm{hfac})}_{2}]$. The molecular orbital calculations of the compound indicate the formation of a mixed-spin-(1/2, 1/2, 5/2) ferromagnetic chain. The temperature dependence of magnetic susceptibility reveals its ferromagnetic behavior. The magnetic specific heat exhibits a double-peak structure and indicates a phase transition at the low-temperature peak. The observed characteristics are explained using the quantum Monte Carlo calculations. Furthermore, the modified spin-wave theory verifies that the double-peak structure of the specific heat significantly reflects the relative ration of the acoustic excitation band and the optical excitation gap.

Synthesis, crystal structure and magnetic properties of mer-tricyanidoiron(III) precursor-based 1D heterobimetallic complexes

Abstract Three new cyanide-bridged heterometallic complexes {{[Cu(S,S-Chxn)2][Fe(bbp)(CN)3]}2·2 H2O} n (1), {{[Cu(R,R-Chxn)2][Fe(bbp)(CN)3]}2·2 H2O} n (2) and {{[Cu(Cycam)][Fe(bbp)(CN)3]}·CH3OH·2 H2O} n (3) (bbp = bis(2-benzimidazolyl)pyridine dianion, Chxn = 1,2-diaminocyclo hexane, cyclam = 1,4,8,11-tetraazacyclodecane) have been assembled from the rarely used mer-tricyanidoiron(III) building block [PPh4]2[Fe(bbp)(CN)3] and three copper(II) compounds. The complexes have been characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. For the chiral enantiomers 1 and 2, the circular dichroism (CD) spectrum was also investigated. X-ray structural analyses revealed that the structures of the cyanide-bridged Fe-Cu complexes 1 and 2 are characterized by two crystallographically independent but structurally very similar homochiral neutral chains, each consisting of the repeating units {[Cu(S,S-Chxn)2][Fe(bbp)(CN)3]} (1) or {[Cu(R,R-Chxn)2][Fe(bbp)(CN)3]} (2). The crystal structure of 3 likewise is build up of chains consisting of {[Cu(Cyclam)][Fe(bbp)(CN)3]} building blocks. The temperature-dependent magnetic susceptibility and field dependent magnetization of the complexes showed antiferromagnetic interactions in complex 1 between the Fe(III) and Cu(II) ions, while complex 3 is ferromagnetic, indicating that the magnetic coupling through cyanide linkage is very sensitive to the structure parameters around the paramagnetic metal ions. These results have been further confirmed by fitting of the experimental data using a uniform chain model, leading to the coupling constants J = −6.35 cm−1, g = 2.08, R = 4.42 × 10−4 and J = 1.24 cm−1, g = 2.09, R = ∑(χ obsd T − χ cald T)2/∑(χ obsd T)2 = 4.67 × 10−4 for complexes 1 and 3, respectively.

Lu26 T 17–x In x (T = Rh, Ir, Pt) – first indium intermetallics with Sm26Co11Ga6-type structure

Abstract Several Lu26 T 17−x In x (T = Rh, Ir, Pt) phases with varying x values were obtained by induction-melting reactions of the elements in sealed tantalum ampoules. All samples were characterized through their X-ray powder diffraction patterns. These compounds crystallize with the tetragonal Sm26Co11Ga6-type structure, space group P4/mbm and Z = 2. The structure of Lu26Pt7.55In9.45 has been refined from single-crystal X-ray diffractometer data: a = 1165.32(5), c = 1547.46(6) pm, wR2 = 0.0895, 2173 F 2 values and 70 variables. The Lu26 T 17−x In x phases are the first indium representatives of the Sm26Co11Ga6 type. They belong to the n = 4 members of Parthé’s A 5n+6 B 3n+5 series, which show different stacking sequences of square prisms and antiprisms. Lu26Pt7.55In9.45 as a lutetium-rich intermetallic compound exhibits a broader range of shorter Lu–Lu distances (341–375 pm). Temperature dependent magnetic susceptibility measurements show Pauli paramagnetism for Lu26Ir8.5In8.5 and Lu26Rh7In10 with room temperature values of the magnetic susceptibility of χ = 1.53 × 10−3 emu mol−1 for Lu26Rh7In10 and χ = 6.54 × 10−4 emu mol−1 for Lu26Ir8.5In8.5.

Intermetallic compounds RE 2Ga2Mg (RE = Tb–Tm, Lu) with Mo2B2Fe-type structure

Abstract The rare earth intermetallic compounds RE 2Ga2Mg with RE = Tb–Tm and Lu were synthesized from the elements in sealed tantalum ampoules in a high-frequency furnace. These rare earth-rich phases crystallize with the tetragonal Mo2B2Fe-type structure, space group P4/mbm and Z = 2. The polycrystalline samples were characterized through their Guinier powder patterns. The structures of Er2Ga2.092(1)Mg0.908(1), Tm2Ga2.037(1)Mg0.963(1) and Lu2Ga2.176(1)Mg0.824(1) have been refined from single crystal X-ray diffractometer data. The refinements revealed small homogeneity ranges (small degrees of Mg/Ga mixing on the 2a sites). The magnesium atoms show square planar coordination by Ga2 dumbbells (282 pm Mg–Ga and 257 pm Ga–Ga in the lutetium compound). Geometrically one can describe the RE 2Ga2Mg phases as 1:1 intergrowth structures of CsCl and AlB2-related slabs of compositions REMg and REGa2. From DFT based calculations, charge transfer from the rare earth and magnesium atoms towards gallium can be illustrated in electron localization function ELF slice planes showing strong localization around gallium in the basal plane as well as along the tetragonal c axis signaling Ga–Ga pair interactions. The site-projected density of states DOS and COOP data further quantify this observation. Temperature dependent magnetic susceptibility measurements show Pauli paramagnetism for Sc2Ga2Mg and Lu2Ga2Mg with low room temperature susceptibility values of 2.1(1) × 10−4 and 1.1(1) × 10−4 emu mol−1, respectively. Ho2Ga2Mg, Er2Ga2Mg and Tm2Ga2Mg are Curie-Weiss paramagnets with stable trivalent rare earth ground states. Antiferromagnetic ordering was detected below the Néel temperatures of T N = 18.6(1) (RE = Ho), 11.9(1) (RE = Er) and 6.4(1) K (RE = Tm). The three compounds show metamagnetic transitions in their 3 K magnetization isotherms. Tm2Ga2Mg exhibits a square loop behavior with small hysteresis.

Improved mechanically induced synthesis of nanocrystalline gadolinium oxymolybdate

A simple one-step mechanically induced route was used for synthesis of Gd2MoO6 (GMO). Single-phase with disordered structure was obtained after 12 ​h of milling. Elemental analysis revealed continuous decomposition of ammonium orthomolybdate. SEM-EDS (energy dispersive X-ray spectrometry) analysis confirmed a homogeneous distribution of Gd, Mo, and O with the atomic ratio 22.2:8.6:69.2% corresponding to Gd1.998Mo0.774O6.228. Aside from conventional X-ray diffraction, we here paid an effort to obtain the information about the local structure of our GMO by 155Gd ​Mössbauer spectroscopy. The analysis of temperature dependence of magnetic susceptibility and field dependence of magnetization of GMO was confirmed to be similar to those of the mechano/thermally synthesized Gd2MoO6 mentioned in our previous study (Tóthová et al., 2019) [1]. Small deviations suggest the presence of nonmagnetic unreacted materials in the starting mixture used in the present mechanosynthesis. We would like to emphasize that the present simplified synthesis without annealing steps leads to GMO with very good quality in the terms of magnetic properties.

Structural and magnetic properties evolution of Cu2xCr2xZr2-2xSe4 for 0.500 ≤ x ≤ 0.650

A series of compound Cu2xCr2xZr2-2xSe4 with x = 0.500–0.650 were prepared by solid-state reaction in sealed quartz tubes. The Rietveld refinements of XRD patterns show that Cu2xCr2xZr2-2xSe4 forms a solid solution of a single phase with the spinel structure (space group Fd3‾m). The lattice parameter (a) gradually decreases with increasing x from 0.500 to 0.625 but does not follow Vegard's law. Later, a increases for x > 0.625. Our investigation revealed the development of clusters with short metal-metal distances. The variation of the cation distribution is discussed as per site preference and the Zr substitution. The magnetic properties of Cu2xCr2xZr2-2xSe4 have been investigated for x = 0.525, 0.600, and 0.625 compositions using SQUID magnetometer. Temperature-dependent magnetic susceptibility indicates a spin-glass for x = 0.525 and 0.600 compositions, but a ferromagnetic ground state for x = 0.625 composition.

A series of new Fe(II) coordination polymers based-on [Hg(XCN)3]− or [Hg(XCN)4]2− (X = S, Se) building blocks: Synthesis, crystal structure and magnetic property

Self-assembly of the tetrahedral metalloligand building block [(HgII(XCN)4]2-, where X ​= ​S or Se, a series of bis-monodentate pyridine-like ligands and iron(II) compounds has afforded seven new heterobimetallic HgII–FeII coordination polymers. Single crystal X-ray diffraction structural analysis revealed the infinite two-dimensional (2D) sheet with different topologies for all the complexes except 3, which belonged to inherent 3D-structure. The results of the temperature dependent magnetic susceptibility investigation over all the complexes discovered the paramagnetic behavior for the high spin iron(II) ion in all the complexes within the temperature range of 2–300K, except complex 6. The thermo- and photomagnetic property study for complex 6 showed incomplete spin crossover (SCO) behaviors with interesting thermomagnetic properties and light-induced excited spin state trapping effect (LIESST). The results show that the ligand field, configurations, rigidity, and polarity of the bridging ligands, as well as the coordination mode with the Fe(II) ion of the building units, are important for the design and synthesis of the targeted coordination polymers.

Synthesis, Structure, and Magnetic Properties of Ditopic Ferrocenylboron-Capped Tris-Pyridineoximate Iron, Cobalt, and Nickel(II) Pseudoclathrochelates

Tris-pyridineoximate iron, cobalt, and nickel(II) pseudoclathrochelates with apical ferrocenyl substituent were obtained in the reasonable yields (50–70%) in a boiling ethanol by the template condensation of 2-acetylpyridineoxime with ferrocenylboronic acid on the corresponding M2+ ion as a matrix. The composition and structure of new ditopic compounds, isolated in the forms of their ionic associates with perchlorate anion, were determined using elemental analysis, UV-vis spectroscopy, MALDI-TOF mass spectrometry, and NMR spectroscopy. According to the magnetometry data, the iron(II) pseudoclathrochelate is a diamagnetic compound, while the temperature dependences of magnetic susceptibility of the nickel and cobalt(II) complexes are characteristic of the high-spin systems with S = 1 and 3/2, respectively. As follows from the X-ray diffraction data for the iron and nickel(II) pseudoclathrochelates, the Ni–N distances (2.15–2.17 Å) are characteristic of the high-spin Ni2+ complexes, while they in its iron(II)-containing analog, slightly exceed of 2 Å, thus suggesting the low-spin state of this ion.

Curie Temperatures and Emplacement Conditions of Pyroclastic Deposits From Popocatépetl Volcano, Mexico

AbstractMost pyroclastic deposits of Popocatépetl volcano were emplaced at high temperatures and have similar mafic to more evolved compositions, suggesting a long‐lived, interconnected magma environment. We performed a magnetic and microscopic study on different eruptive sequences <14 ky in age and found that temperature and field dependence of magnetic susceptibility are suited to separate eruption phases. We observed homogeneous titanomagnetite with Curie temperatures (TC) of 50–200°C and 200–400°C, together with different amounts of oxy‐exsolved titanomagnetite with TC ∼ 570°C. Some block‐and‐ash flow deposits show remarkably irreversible TC in heating and cooling branches with a positive ΔTC (TC heating–TC cooling) of up to 130°C in the center. The central part of this sequence is characterized by decreasing magnetic susceptibility and low field dependence of magnetic susceptibility (<10%), which is atypical for ulvöspinel‐rich titanomagnetite. The nonreversibility of heating and cooling runs measured with rates of around 10 K/min is probably related to vacancy‐enhanced nanoscale chemical clustering, which seems to occur preferentially during rapid quenching, possibly combined with subtle maghemitization. In contrast, pumice layers have the highest field dependence (∼20%) and contain Ti‐rich and intermediate titanomagnetite with TC < 100 and ∼300°C, which are in line with mafic and more evolved magma composition. In intermediate phases, irreversibility of TC is more common but with a relatively low ΔTC of ±20°C. We suggest that magneto‐mineralogy in pyroclastic density currents is complex but offers a complementary tool to the paleomagnetic directional analysis for emplacement temperature and contribute information on the volcanic material history and their emplacement conditions.

Understanding the magnetic response of the Quantum Spin Liquid compound 1[formula omitted]-TaS[formula omitted

1T-tantalum disulphide (1T-TaS2) is a promising material to realize quantum spin liquid state. Here, we take a closer look on the temperature dependent magnetic susceptibility of 1T-TaS2 at low magnetic fields to understand the formation of local magnetic moment in this system and its response as a function of temperature and field. We found that the susceptibility increases with reducing temperature even in the nearly commensurate charge density wave (CDW) phase, which exhibits metallic conductivity and hence is expected to exhibit temperature independent Pauli paramagnetic susceptibility. It indicates that local moment starts forming in the nearly commensurate CDW phase itself, which is well above the temperature where evidence of Mott insulating state appears in resistivity measurement. In the commensurate CDW phase, susceptibility significantly deviates from the Curie–Weiss law. Below T = 10 K, temperature dependence of susceptibility indicates the formation of random singlet state in 1T-TaS2.

Low-temperature magnetic susceptibility of ErAl3(BO3)4 single crystal: Evidence of antiferromagnetic spin-spin correlations

Temperature dependence of magnetic susceptibility of the ErAl3(BO3)4 single crystal was measured in the temperature range of T = 2−15 K at the external magnetic field of H = 100 Oe applied along the a and c crystal-lographic axes. The influence of spin-spin correlations on the magnetic susceptibility has been identified. It was estimated that the value of Curie-Weiss temperature is θAF ≈ −0.45 K.

Structure and properties of the Sr2In1-xSnxSbO6 double perovskite

A series of n-type oxide double perovskite semiconductors, Sr2In1-xSnxSbO6 (0 ​≤ ​x ​≤ ​0.3) has been synthesized; Sn4+ partially substitutes for In3+. 121Sb and 119Sn Mössbauer spectroscopy are employed to investigate the B-site cation ordering because this issue cannot be resolved by conventional diffraction techniques alone. Rigid ordering between In3+/Sn4+ and Sb5+ sites is revealed by the spectroscopic method, and hence in combination with the structural parameters extracted from the XRD structural refinements, the crystallographic structure of this series of compounds is depicted. The temperature dependent magnetic susceptibilities, band gaps, and carrier type are characterized, and the calculated band structure is presented.

LiYbSe2: Frustrated Magnetism in the Pyrochlore Lattice.

Three-dimensionally (3D) frustrated magnets generally exist in the magnetic diamond and pyrochlore lattices, in which quantum fluctuations suppress magnetic orders and generate highly entangled ground states. LiYbSe2 in a previously unreported pyrochlore lattice was discovered from LiCl flux growth. Distinct from the quantum spin liquid (QSL) candidate NaYbSe2 hosting a perfect triangular lattice of Yb3+, LiYbSe2 crystallizes in the cubic pyrochlore structure with space group Fd3m (No. 227). The Yb3+ ions in LiYbSe2 are arranged on a network of corner-sharing tetrahedra, which is particularly susceptible to geometrical frustration. According to our temperature-dependent magnetic susceptibility measurements, the dominant antiferromagnetic interaction in LiYbSe2 is expected to appear around 8 K. However, no long-range magnetic order is detected in thermomagnetic measurements above 70 mK. Specific heat measurements also show magnetic correlations shifting with applied magnetic field with a degree of missing entropy that may be related to the slight mixture of Yb3+ on the Li site. Such magnetic frustration of Yb3+ is rare in pyrochlore structures. Thus, LiYbSe2 shows promise in intrinsically realizing disordered quantum states like QSL in pyrochlore structures.

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe 2 Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe ₂ Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Low temperature magnetic properties of Gd doped CaMnO3

The Gadolinium (Gd) doped CaMnO 3 or Ca 0.7 Gd 0.3 MnO 3 (CGMO), structural and magnetic behavior were investigated through the X-ray diffraction and DC magnetization measurements. The high quality CGMO polycrystalline were prepared through the multiple heat treatment of solid-state reaction method. The X-ray diffraction measurement confirms the formation of single-phase with orthorhombic structure and Pnma space group. Scanning electron microscopy study reveals the surface morphology and average grain size about 2 μm. Rietveld refinement techniques were used to obtain the room temperature (RT) atomic parameters. The obtained atomic parameters of CGMO are a = 5.3465(4) Å, b = 7.5001 (5) Å and c = 5.3184 (4) Å are well matching with CaMnO 3 . Temperature-dependent (4–300 K) magnetic susceptibility (M)T measurements were carried out on CGMO at 500 Oe. Low-temperature magnetic susceptibility (ZFC and FC curves) confirms the magnetic transition i.e, paramagnetic to antiferromagnetic phase (T N ) at 67 K, and surprisingly below 10 K magnetic moments are increasing, it may be due to the formation of weak ferromagnetic ordering. Curie Weiss fitting was carried out on low-temperature inverse susceptibility of field cooled curve which shows hump around 67 K and below 10 K. From the Curie-Weiss fitting paramagnetic curie constant θp ∼ -72 K extracted, which is a clear indication of the formation of antiferromagnetic ordering and below 10 K weak ferromagnetic interaction.

Anomalous electrical transport behavior in the vicinity of the first-order magnetostructural transition in the giant magnetocaloric Gd4ScGe4

Magnetic, specific heat, and electrical transport measurements of ${\mathrm{Gd}}_{4}{\mathrm{ScGe}}_{4}$ single crystals reveal sharp, discontinuous, nearly anhysteretic first-order magnetostructural transformation at ${T}_{\mathrm{C}}=63\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The electrical resistivity exhibits two distinct regions where it increases with decreasing temperature: between ${T}_{\mathrm{C}}$ and 120 K, as well as below 3 K; electronic transport remains conventionally metallic at all other measured temperatures, up to 325 K. The dispersion of charge carriers due to electron-paramagnon scattering is the likely reason for the observed anomalous transport above ${T}_{\mathrm{C}}$. Additionally, the existence of intermediate lattice states near the transition recognized by the spike in the interslab Ge-Ge distances is expected to reduce the mean free path of the electrons contributing to the unusual behavior of the electrical resistivity between ${T}_{\mathrm{C}}$ and 120 K. Beyond conventional electronic and lattice terms, the third component of likely magnetic origin contributes to the low-temperature heat capacity; the presence of spin waves may be responsible for the increased electron-magnon scattering below 3 K. Minor magnetocrystalline anisotropy is observed with the $b$ axis as the easy magnetization axis in ${\mathrm{Gd}}_{4}{\mathrm{ScGe}}_{4}$. A negative deviation from linearity in the temperature dependence of the inverse magnetic susceptibility is detected below 150 K.

Dispersion medium crystallization effect on the magnetic susceptibility of ferrofluids

Ferrofluids (magnetic colloids) with a dispersion medium crystallizing with a decrease in temperature are investigated. Temperature dependences of the dynamic magnetic susceptibility of such ferrofluids were measured. For comparison, similar susceptibility dependences of ferrofluids with a dispersion medium that does not form a crystalline structure when solidified by cooling are also presented. It is demonstrated that crystallization of the dispersion medium leads to an inhomogeneous spatial distribution of dispersed phase particles and the formation of regions of high particle concentration. This does not happen in the case of colloids with a dispersion medium that does not form a crystalline structure. It is concluded that the formation of regions of high concentrations of dispersed phase particles during crystallization is the cause for a jump in colloid magnetic susceptibility. This conclusion refutes the previously existing opinion that the reason for the jump in the susceptibility of a ferrofluid at the temperature of transition to a solid state is the blocking of Brownian degrees of freedom of particles.