Magnetism

Magnetic susceptibility of one-dimensional spin chains S(Ni$^{2+}$)=1 single crystal Y$_2$BaNiO$_5$ in the region of 1.85–800 K

V. I. Petinov^a, A. B. Kulakov<sup>b

a</sup> Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, Chernogolovka, Moscow region
^b Osipyan Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow region

Abstract: The magnetic susceptibility of $\chi(T)$ one-dimensional spin chains (OSCs) of a single crystal Y$_2$BaNiO$_5$ was first studied in the range of 1.85–800 K. In the region from 800 to $\sim$520 the OCC exhibits Curie–Weiss paramagnetism, in which $\chi_0(T)=C/(T+800)$, where C is the Curie constant, with an effective magnetic moment of $\theta_{\mathrm{eff}}$ = 3.75 $\mu_{\mathrm{B}}$. With a decrease from 520 to 40 K, the susceptibility changes as a Halden magnet with a gap $\Delta$ = 117 K, $\chi(T)=\chi_0(T)\exp(-117/T)$. Below 40 K $\chi(T)$ grows again according to the Curie–Weiss law with $\theta_{\mathrm{eff}}$ = 3.75 $\mu_{\mathrm{B}}$, $\theta_{i1}$ = -3 K and $n_{i1}$ = 9.3$\cdot$10$^{19}$ spins S(Ni$^{2+}$) = 1 per mole in a crystal grown in an oxygen-free environment; and $\theta_{i2}$ = -1.3 K, and $n_{i2}$ = 4.6$\cdot$10$^{19}$ spins S(Ni$^{2+}$) = 1 after annealing this crystal to 1000$^\circ$C in air and its subsequent slow cooling. Such a change in the “impurity” contribution to $\chi(T)$ of the OCC is presumably due to a lack of O$_2$ in a significant proportion of the terminal spins in the OCC of a single crystal.

Keywords: energy gap, SQUID measurements in the region of 1.85–800 K, end spins, breaks in the spin chain.

Received: 14.03.2023
Revised: 14.03.2023
Accepted: 16.03.2023

DOI: 10.21883/FTT.2023.05.55497.34

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